survey of the irrigation potential of the lower tana river basin kenya

^
ISHIC LIBRAE?
KE - 1968.06
Wageningen
The Netherlands
o •- —4
FAO/SF: 53/KEN-3
SURVEY OF THE IRRIGATION POTENTIAL
OF THE LOWER TANA RIVER BASIN
V
KENYA
FINAL REPORT
Volume I
GENERAL
UNITED NATIONS DEVELOPMENT PROGRAMME
)OD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
is>

* • • [ "=»
VOLUMES OF THE FINAL REPORT
Volume I --.. •' "--.',, ^
The General Report-ThéSGeneral Report is issued by the Food and. Agriculture Organization
of the United Nations acting^ as executing agency for the -project on' behalf of
the' United Nations Development Programme. The volume contains the essential story of
the studies, carried out during the survey and the agency's conclusions and recommendations
based thereon., ' " ' ' * . - - ' '
Volumes II to VII

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SURVEY OP THE IRRIGATION POTENTIAL OP
THE LOWER TANA RIVER BASIN
KENYA
158*30

Survey of the Irrigation Potential of
the Lower Tana River Basin
KENYA
Final Report
Volume I
General
PAO/SPt
Report prepared for the
Government of Kenya "by the
Pood and Agriculture Organization of the United Nations
aoting as exeouting agenoy for the
United Nations Development Programme
United Nations Development Programme
Pood and Agriculture Organization of the United Nations
Rome, 1968
: I._'..,J •. . .. ..(
K E
(sÖ. a(o
; w 'Oanlnnnn, The Mo norlands 1
i

- V -
ABSTRACT
This report describes a project conducted by the Government of Kenya, with the
assistance of the United Nations Special Fund*and the Pood and Agriculture Organization
of the United Nations, to assess the irrigation potential of the Lower Tana
river basin. The Government's request for assistance was approved at the Kay 1$62
session of the Governing Council of the United Nations Special Fund.
The Consortium of International Land Development Consultants of Arnhem, the
Netherlands, and Acres International Ltd. of Niagara Falls, Canada, were commissioned
by the Food and Agriculture Organization of the United Nations to undertake the
survey. This document forms the General Report on the project prepared by FAO as
executing agency.
A Plan of Operation for the implementation of the projeot was agreed and signed
on behalf of the Government of Kenya, the United Nations Special Fund and the Food
and Agricultural Organization on 2 May 1963. The UNDP allocation to the projeot
amounted to US $ 1,033,400 and this covered the cost of personnel, contractual
servioes, fellowships and equipment. The Government contribution in kind, which
amounted to some US $ 714,200, oovered the oost of counterpart personnel, local equipment
and supplies, housing and office buildings, land and transportation.
The possibility of large scale development of this region involved investigations
of storage sites and water requirements in the upper portions of the catchment.
Therefore, it was necessary to investigate the entire catchment as one hydrological
unit and to oonsider the part that would be played by the development of hydroeleotrio
power.
Field operations were started in August 1963 and were oompleted in August 1966.
The work oarried out inoluded» mapping the irrigation project area in the lower Tana
basin and the middle reaches of the river} geologio and geophysical examination of
foundation conditions at potential storage and diversion dam sites} soils and vegetation
surveys} agronomio and irrigation experiments and hydrometeorolôgical appraisals.
Preliminary engineering plans and designs, with cost estimates, and an economic appraisal,
were prepared for proposed irrigation development. Many miles of dryweather
roads and tracks were constructed to facilitate the surveys and to permit
aocess throughout the project area.
Nine fellowships were awarded during the course of field operations, in irrigation
engineering, agronomy and management, and in hydraulic engineering. The first
fellowship was taken up in September I965 and the last in July I966. The countries
to which the fellows were sent for study included U.S.A., Canada, Sudan, Netherlands
and Israel.
» Assistance to the projeot was provided by the United Nations Spooial Fund until
1 January 1966, On that date the Special Fund and the Expanded Programme of
Technioal Assistance were merged into the United Nations Development Programme,
which oontinued to provide assistance to this projeot.

vi
The findings of the survey confirm the results of previous investigations,
which have shown the possibilities of developing hydro-electric power at a succession
of points in the middle reaches of the Tana river. Suoh a network could
provide an installed capacity of 865 megawatts at a oapital oost of nine million
pounds sterling. It is expected that the inclusive cost per kilowatt of such
development would he lower than that of power from alternative thermal stations*
The demand for power in Kenya is expected to rise to 800 megawatts hy the year
2000. and as the present potential for hydro-eleotrio power from sources other
than the Tana river is only 18 megawatts, this points to the necessity for developing
power on the Tana river as soon as possible,,
In its lower reaches, the firm flow of the Tana river is shown to he 1,100
cubio feet per second, whioh is enough to irrigate 100,000 aores of land. The
regulation of flows for power would enahle the firm flow downstream to he inoreased
to 2,800 cubio feet aperrsecond hy the year 2000, enough for 250,000 acres of :
irrigation, ultimately, hy diverting flows from the Athi river, 330,000 aores of
suitable soils could be irrigated.
On groundwater, the report concludes that there is little or none available
in the projeot area, except in the perched water table to be found in the Tana
flood plain adjoining the river channel.
Since the cost per acre of irrigation development will be high, field trials
were concentrated on cash crops which could bring in fair to good returns. Except
for cotton, whioh had consistently given good yields over a number of years, trials
of other crops had not been carried out long enough to reaoh firm conclusions.
More investigation and testing remains to be done before a really sound oropping
pattern can be developed. Therefore, the report recommends, as a first step, the
setting up of a Research and Training Centre to be supplied with irrigation water
by pumping. This centre would be the first stage of development of the ultimate
irrigation scheme, and at the same time would investigate the cropping patterns,
conditions of tenancy and of cultivation, financial arrangements and all other
points involved in the successful development, operation and management of suoh
large scale schemes.
Concurrent with this first stage of development, the report recommends the
setting up of a semi-autonomous organization, to be called "The Tana River Irrigation
Authority" and to take charge of the soheme from the beginning. Its functions
would include construction and operation, marketing, research, extension and
training, mechanized cultivation and the processing of crops.

FRONTISPIECE
ABSTRACT
CHAPTER I INTRODUCTION
- vix -
TABLE OF CONTENTS
1.1 Origin of the Project
1.2 The Plan of Operation
1.3 Field Operations
1.4 Acknowledgements
CHAPTER II SUMMART OF CONCLUSIONS AND RECOMMENDATIONS
A. CONCLUSIONS
2,1: The Tana River and Its Water
Resources
2.2 The Use.of Water for Power
and Irrigation
2.3 Lands Available
2.4 Costs of Irrigation and Agronomio
Considerations
2.5 Scheme of Development for
Irrigation
2.6 Infrastructure and Secondary
Developments
2.7 Organization and Management
2.8 Phasing of Development of
Irrigation
2.9 Economic Evaluation
2.10 Financial Analysis
2.11 Recovery of Costs from Cultivators
2.12 Size of Holdings
2.13 Animal Husbandry
B. . RECOMMENDATIONS
2.1 Need to Reappraise the Scheme for
Irrigation Development
2.2 Pilot Scheme
2.3 Tana River Irrigation Authority
2.4 Further Studies
2.5 Subsequent Action

- viii -
CHAPTER III THE COUNTRY AND THE PROJECT AREA
3.1 The Country
3.2 The Project Area
CHAPTER IV METEOROLOGY AND HYDROLOGY
4.1 Hydrometeorologio/ Data
4.2 Hydrometeorologio Analyses
CHAPTER V SURVEYS, GEOLOGY AND ENGINEERING COST DATA
5.1 Topographic Mapping
5.2 Geologic Surveys
5.3 Cost Estimating Data
CHAPTER VI SOILS AND VEGETATION
CHAPTER VII AGRONOMIC STUDIES
6.1 Semi-detailed Soil Surveys
6.2 Detailed Soil Survey
6.3 Vegetation Survey
6.4 Land Classification
6.5 Reclamation
7.1 Cotton Experiments and Observations
7.2 Experiments and Observations on Crops
other than Cotton
7.3 Irrigation Trials
7.4 Animal Husbandry
CHAPTER VIII AGRO-ECONOMIC STUDIES
8.1 Markets and Price Levels
8.2 Land Tenure
8.3 Tenant Income and Labour Requirements
Page No
16
16
17
30
30
32
41
41
42
44
46
46
47
47
49
51
55
56
56
60
60
62
62
65
66

CHAPTER IX AGRICULTURAL DEVELOPMENT
- ix
9.1 Cropping Pattern
9.2 Farm Size and Layout
9.3 Requirements for Labour and Machinery
9.4 Value and Cost of Agricultural
Production
9»5 Processing of Farm Products
CHAPTER X POWER POTENTIAL AND MARKETS
10.1 Power Resources of Kenya
10.2 Present Kenya System
10.3 Load Growth Forecast
10.4 Comparative Cost of Energy
CHAPTER XI WATER RESOURCES PLANNING AND POTENTIAL
CHAPTER XII POWER DEVELOPMENT
11.1 Water Resources for Power Development
11.2 Water Resources for Irrigation
Development
11.3 Implications of Water Resources
Development
12.1 Selection of Storage and Power Sites
CHAPTER XIII IRRIGATION DEVELOPMENT
13.1 Potential Development -
Layout of Irrigation Network
13.2 Potential Development -
Groundwater Conditions and Drainage
13.3 Land Preparation
13.4 Road Network
13.5 Ko'rokora Dam
13.6 Capital Costs —
Irrigation Development
Page Ho.
67
67
69
69
71
73
74
74
70
77
79
82
82
63
90
92
93
105
106
112
112
113
114
114

- X -
13.7 Research and Training Centre
13.8 Pilot Scheme - First Stage of
Development
CHAPTER XIV INFRASTRUCTURE A1ID SECONDARY DEVELOPMENT
14.1 General
14.2 Requirements
14*3 Other Aspects
I4.4 Processing
CHAPTER XV ORGANIZATION AND MANAGEMENT
15.1 General
15.2 Specific Points
CHAPTER XVI ECONOMIC EVALUATION
16.1 Internal Rates of Return
16.2 Recovery of Costs from Beneficiaries
16.3 Tenant Income
16.4 Financial Analysis
16.5 Estimate of Total Required Investment
16.6 Foreign Currency Aspect of
Project Development
16.7 Conclusions
CHAPTER XVII FURTHER STUDIES AND INVESTIGATIONS
17.1 Requirements
17.2 Ways and Means
Page No.
116
116
120
120
121
122
123
124
124
125
127
128
142
145
146
151
151
160
162
162
164

- 3d.
Page No.
APPENDIX I PLAN OF OPERATION 165
APPENDIX II LIST OF PROJECT STAFF 179
APPENDIX III FELLOWSHIP AWARDS l80
APPENDIX IV REFERENCES l8l

- aüLi
LIST OF TABLES
No. Page No.
2-1 Power Development on the Middle Tana 5
2-2 Irrigation Development - Internal Rates of
Return 11
3-1 Long—term Average Flow - Tana River and
Tributaries 23
4-1 Net Discharges at Seven Forks (Confluence) and
at Koreh 33
4-2 Long-term Average Flow and Net Available
Flow - Tana River and Tributaries 34
4-3 Estimates of "Design Flood" Peak Discharge
Used in the Studies 35
4-4 Estimates of Diversion Flood Peak Discharge
Used in the Studies 36
4-5 Average Annual Evaporation and Rainfall
Rates Used in Evaluating Potential Storage
Reservoirs 37
4-6 Monthly Estimates of Potential Evapotranspiration
for the Project Area 37
4-7 Monthly Recurrence Intervals of Effective
Rainfall at Galole 38
4-8 Recurrence Intervals of Maximum Rainfall in the
Project Area 39
4-9 Sedimentation Estimates at Potential Storage
Sites 40
6-1 Soil Classification 48
6-2 Classification óf the Vegetation into
Associations 50
6-3 Land Suitability Classification - Project Area
(1) and (2) 52-53
6-4 Soil Suitability Classification - Research and
Training Centre 54
8-1 Population Orowth Estimates - Kenya 63
8-2 Projected Cotton Requirements for Kenya in Tons
of Cotton Lint for High and Low Projections
of Population Orowth 64
9-1 Direct Costs of Agricultural Production 71
9-2 Estimation of Farm Income 72
9-3 Quantities of Produce to be Processed (30,000
acre district) 73
11-1 Long-rterm Average Flows and Design Discharges 83
11-2 Firm Flows and Energy Outputs - Tana River
Development Mutonga II Sequence D 84

•xiii
LIST OF TABLES (Cont«d)
go. Page No.
11-3 Monthly Bet Water Requirements 85
11-4 Monthly Irrigation Potential of Diverted Plow
at Korokora Irrigation Potential 85
11-5 F 10 * Availability at Korokora 86
12-1 Head, Flow and Power Potential of the Middle
Tana 94
12-2 Estimates of Capital Cost - Tana River Power
Project 97
12-3 Mutonga II - Sequences of Development 98
12-4 System Power Output and Growth with Variations
in Load Growth and Net Water Availability 99
12-5 System Power Output and Cost with Athi River
Diversion 100
I3-I Net Irrigahle Areas Commanded by Section
Feeders 111
13-2 Estimates of Capital Costs - Irrigation Development
II8
13-3 Research and Training Centre - Estimate of
Capital Cost 119
16-lA Investments for Irrigation Development
Rate 1 - 250,000 Acres 129
16-lB Investments for Irrigation Development
Rate 2 - 250,000 Aores 130
16—lC Investments for Irrigation Development
Rate 1 - 300,000 Acres 131
16-lD Investments for Irrigation Development
Rate 2 - 300,000 Acres 132
16-2A Irrigation Development - Annual Costs and
Benefits - Rate 1 - 250,000 Aores 133
16-2B Irrigation Development - Annual Costs and
Benefits - Rate 2 - 250,000 Aores 134
16-2C Irrigation Development - Annual Costs and
Benefits - Rate 1 - 300,000 Aores 135
16-2D Irrigation Development — Annual Costs and
Benefits - Rate 2 - 300,000 Acres 136
16-3 Internal Rates of Return 137
I6-4 Specimen Representative Finanoial Analysis
Irrigation Development 150

•xiv-
LIST OF TABLES (Cont'd)
Ko, Page Ko,
16-5A Total Required Investment Hate 1 - 250,000 Acres 152
16-5B Total Required Investment Rate 2 - 250,000 Aores 153
16-5C Total Required Investment Rate 1 - 300,000 Acres 154
16-5D Total Required Investment Rate 2 - 300,000 Acres 155
16-6A Foreign Currenoy Aspects of Irrigation Development
Rate 1 - 250,000 Aores 156
16-6B Foreign Currency Aspects of Irrigation Development
Rate 2 - 250,000 Acres 157
16-6C Foreign Currency Aspeots of Irrigation Development
Rate 1 - 300,000 Acres 158
16-6D Foreign Currenoy Aspects of Irrigation Development
Rate 2 - 300,000 Acres 159
^

- XV -
LIST OP PLATES
No. Page Wo.
1
2
3
4
5
6
7
10
11
12
13
14
15
(Sheet 1 and 2)
16 (Sheet 1 to 3)
17
18
19
20
21
22 (Sheets 1 and 2)
23 (Sheets 1 and 2}
24 (Sheets 1 and 2)
Tana River Basin 19
Profile of Tana River 21-22
Average Annual Isohyetal Pattern 25
Eastern Kenya General Geology 27
Hydrograph of Average Monthly Discharges
Tana River at Kamburu 31
Proposed Crop Pattern 68
Schematic Arrangement of Rotations and
Crop Phasing Related to Farm Holdings 70
Nairobi and Western Kenya System -
Electrical Demand - Peak Load Forecast 78
Cost of Energy from Thermal Installation
at Mombasa 80
Rates of Irrigation Development 87
Comparison between Plow Availability and
Irrigation Demand at Korokora 89
Power Development - Middle Tana 96
Development Sequence Mutonga II D -
Installation Schedule - Load Growth
Rate 1 102
Development Sequence Mutonga II D -
Installation Schedule - Load Growth
Rate 2 103
Mutonga Sequence II D - Cumulative
Capital Expenditure IO4
Layout of Project Area IO7-IO9
Distribution System - Layout of Irrigation
Blook and Typical Seotions 115
Korokora Diversion Dam- General Arrangement
Pull Supply Level 463 Feet 117
Irrigation Project - Schematic Management
Organization Chart 126
Irrigation Development - Streams of
Investment 138
Irrigation Development - Annual Costs 139
Irrigation Development - Annual Benefits
and Expenditures to Authority I4O-I4I
Internal Rates of Return 143-144
Total Annual Benefits and Expenditures
of Irrigation and Processing 147-148

1.1 Origin of the Project
- 1 -
INTRODUCTION
CHAPTER I
The need to develop the irrigation potential of the lower Tana river in the
Republic of Kenya has long been recognized by the Government. Certain investigations
had already been carried out prior to the inception of this project. For example,
a detailed study of the water resource potential of the upper catchments of the river
for both irrigation and hydro-electrio power development had been carried out by
Messrs. Alexander Gibb and Partners. The middle Tana had been investigated by
Messrs. Balfour Beatty, consultants as to the potential of this section for hydroelectric
power development.
The lower Tana, with its extensive areas of desert soil lying close to a good
source of irrigation water, appears to be a natural region for agricultural development
and for settling surplus peasant population from densely populated areas in
other parts of Kenya. Any large-soale development of this region would involve
investigations of storage sites and water requirements in the upper portions of the
oatchment. Therefore, for the purposes of this project it was neoessary to consider
the entire oatchment as one hydrological unit in planning development of the lower
portion for irrigation.
The Governing Council of the United Nations Special Fund - ' agreed to a request
by the Government for assistance in the Tana basin studies, at its May 1962 session.
The Food and Agriculture Organization of the United Nations, appointed as the
executing agenoy, in turn appointed as co-operating consultants the Consortium of
International Land Development Consultants, N.V., of Arnhem, the Netherlands, and
Acres International Limited, of Niagara Falls, Canada. The Government appointed its
Ministry of Land Settlement and Water Development as the Government Counterpart
Agency. The UNSF authorized operations to commenoe in June 1963; the project became
operational on 4 August 1963 and oonoluded in August 1966.
l/ Assistance to the projeot was provided by the United Nations Speoial Fund
until January I966. On that date the Speoial Fund and the Expanded Programme
of Technical Assistance were merged into the United Nations Development
Programme which continued to provide assistance to this projeot.

- 2
In June 19^3 a preliminary mission, consisting of representatives of FAO and
the consultants, undertook a pre-project evaluation, assessed requirements for equipment,
and established limits for the irrigation project area so that the essential
ground control surveys for mapping could proceed.
1.2 The Plan of Operation
General guidelines for the survey of the irrigation potential of the lower Tana
basin are set forth in the Plan of Operation as agreed and signed between the Government
of Kenya, the United Nations Special Fund, and the Food and Agriculture Organization
on 2 May, 1963. The Plan of Operation is attached as Appendix I to this report.
Taking into account subsequent amendments to the Plan of Operation, it will be observed
that the total cost of the projeot was of the order of US 8 1,747,600. The UNDP allocation
of US $ 1,033,400 was in the form of technical personnel and contractual
services, fellowships and equipment. Details of projeot personnel and fellowships are
provided in Appendix II and III of this report.
The Government counterpart contribution, estimated at U3 % 714»200 was in the
form of counterpart technical and administrative personnel, local equipment and
supplies, housing, office buildings, and transportation.
1.3 Field Operations
All of the necessary field investigations were set in hand with the full cooperation
of the Kenya Government. Some early delays and difficulties were experienced
due to disruption of normal road communications through flooding and by the disturbed
conditions in the area under investigation at the time. The delays caused through
deferment of oertain investigations were largely overcome through the re-scheduling of
operations, and although the field assignments for several members of the project team
had to be extended, no substantial overall delay was experienced in completing the
studies.
The investigations carried out for this survey included mapping the portion of
the lower Tana basin containing the irrigation project area, and the middle reaches
of the riverj geologio and geophysical examination of foundation conditions at potential
storage and diversion damsites; soils and vegetation surveys throughout the
project lands} agronomio and irrigation experiments] and hydrometeorologic appraisals,
network extension and analyses. Many miles of dry-weather roads and tracks were
constructed to facilitate the surveys, permitting access throughout the irrigation
project area and to various locations along the main river and its tributaries.
Extensive laboratory analyses in the fields of soil chemistry and geoteohnics were
undertaken. All of these, together with the related engineering, agricultural and
economio studies, form the basis for evaluation of project potential as described in
this report.
1.4 Aoknowledgements
The Food and Agriculture Organization wishes to place on record its sincere appreciation
of the assistance of the Government of the Republio of Kenya and of the many
individuals and organizations who contributed materially to the successful execution

-3-
of the survey. The keen interest and support shown by the Minister of Agriculture,
the Hon. B. McKenzie, his Permanent Secretary, Mr. O.K. Kariithi, the Tireotor of
Agriculture, Mr. P.T. Mirie, and other officers of his staff are greatly appreciated;
also, special thanks are due to the Government's Co-Manager, Mr. G. Manig, and his
predecessor, Mr. I.D. Watts, and all of the Government counterpart staff assigned
to the survey, who ensured that the numerous requirements of the survey were provided
in full. The guidanoe provided hy the Tana River Steering Committee has heen particularly
helpful in clarifying Government policy and arranging for inter-departmental
co-operation in the execution of the survey.

A. CONCLUSIONS
- 4 -
SUMMARY OF CONCLUSIONS AND RECOMMENDATIONS
2.1 The Tana River and Its Water Resources (see Chapter III)
CHAPTER II
The Tana river is the largest perennial river in Kenya and its water resources,
indicated below, offer the greatest potentials for hydro-electric power generation
and irrigated agriculture in the country, as the following details of long-term flow
show:
Place Catchment Estimated Present reser­ Present
Kainburu
Grand Falls
Koreh
Garissa
long-term
average flow
vation for upper
catchment
long-term
average flow
sq.miles cusecs cusecs cusecs
3,500
6,800
9,500
12,500
3,125
5,130
5,580
4,750
530
530
530
530
2,595
4,600
5,050
4,220
The actual flows of course vary widely above and below these long-term average
rates, both from day to day, and from year to year. Of the 530 cusecs now reserved,
up to 4OO cusecs may be released, if so decided by the Government. In addition,
some diversion of water from the upper Athi river to the Tana river, via the Thika
river, might provide up to 757 cusecs more.
2.2 The Use of Vater for Power and Irrigation (see Chapters IV and XI)
It is evident that whilst hydro-eleotrio power can be developed independently,
large scale irrigation of the lower basin is dependent upon the upstream control of
flows necessary for power generation. The optimum power complex would in fact remain
the same, even if irrigation were not developed. Thus, the two major uses of the
water resources of the Tana river are mutually compatible.

- 5 -
Although it is apparent that the rate of development of irrigation is to some
extent dependent upon 'the rate of growth of the power system, this appears to he of
little practical significance, as a growing demand for power already exists. If
this demand is met by development of the hydro-electric resources of the Tana, it is
bound to provide the necessary flow control in advance of any reasonable schedule
of irrigation development which may he foreseen.
The power system envisaged would utilize to a high level the head and flow of
the middle Tana, through a complex of projects, the main features of which are summarized
in Table 2-1. The power system defined in this table does not include the
additional 131 megawatt potential that could be developed by releasing some 400
cubic feet per second (cusecs) of upstream allocations.
Project Estimated
capital cost*
Seven Forks**
Kiambere
Mutanga
Grand Falls
Adamson's Falls
Koreh
Athi Diversion
Table 2-1 - Power Development on the Middle Tana
£ E.A.
(millions)
63.91
23.70
22.12
16.39
14.77
17.58
2.12
Gross
head
ft
1,005
334
268
I85
123
177
I6O.59 2,092
Long-term
firm flow
cusecs
2,730
2,730
3,850
4,180
4,550
4,410
575
Installed
capacity
MW
320
I92
112
89
65
87
Annual
energy
production
GWh***
1,630
575
63O
494
359
479
865 4,167
* Including capitalized value of accumulated operating defioits during
development period; for load growth rate 1.
** Seven Forks development assumed as Confluence projeot to FSL 3,455 feet,
plus Kindaruina as under construction.
*** GWh - gigawatt/hour

-6-
Sequential development of the power complex would result in progressive control
and regulation of river flows, such that a small reservoir would be sufficient to
re-regulate the outflows from the power system in line with the water demands of any
irrigation complex contemplated.
Without any regulation, the minimum flow to be expected at Koreh is estimated
to be, in most years, at least 1,000 cusecs. Following the successive development of
the power complex, the resulting firm flows at Korokora estimated to become available
for irrigation are as follows:
Site of Power
Development
Firm outflow Est, firm
flow entering
downstream
cusecs cusecs
Confluence 2,160 1,600
Mutonga 3,480 450
Grand Falls 3,810 150
Adamson's Falls 3,980 negligible
Koreh 3,480 —
Net firm flow
expected to be available
for diversion at Korokora
cusecs
2,150
2,900
2,950
2,950
2,810
These figures allow for average amounts of 830 cusecs natural loss from Koreh
to Korokora, 100 cusecs compensation flow at Korokora, and 100 cusecs loss from
evaporation in Korokora reservoir (see also Chapter XI ant* XIl).'
An irrigation complex is considered which would technically extend to 300,000
acres, for which it would be necessary to control and divert flows to the proposed
irrigation area situated on the right bank of the lower river by means of a dam
at Korokora. A layout has been prepared for the irrigation complex and preliminary
designs have been made for the diversion dam.
2,3 Lands Available
Although the topography of the lower basin presents no special problems in the
design of gravity irrigation systems, patches of suitable and unsuitable soils are
intermingled, and this precludes utilization of about half of the lands under command
of the diversion dam and the main supply canal. The following suitability classes
and amounts of land have been identified.
Cla3s
1
2
3
Description
Highly suitable
Suitable
Fairly suitable
Gross Acres
18,000
224,000
323,000
It appears that the amounts of water to be made available, rather than the
extent of land, will be one ruling factor in determining the ultimate potential
development of irrigation.

- 7 -
2.4 Costs of Irrigation and Agronomio Considerations (see Chapters VII, VIII and IX)
During the project studies, two levels of possible irrigation development were
considered, namely 250,000 acres, and 300,000 acres. The estimated direct capital
expenditure necessary worked out at 53 million and 60 million East Africa pounds
respectively (see details in section 2.5 below). Direct investments in institutional
and social infrastructure were estimated to cost an additional £E.A. 400 per net acre,
and processing facilities a further £E.A. 200 per net acre. The foregoing did not
include the costs of supporting productive activities such as forestry and fisheries,
nor the external infrastructure related to project development.
Since the cost of irrigation development per acre seemed to be so high, attention
was concentrated on cash crops which could offer fair to good returns.
Agronomic trials at Galole covered cotton, sugar cane, kenaf, groundnuts, castor,
beans, maize, sorghum, rice, and fodder crops. Except for cotton, already well
established at Galole, the tests made could not be sufficiently comprehensive in the
time available, and more testing remains to be done. However, on the studies made
and information available, a cropping pattern was evolved which included cotton,
sugar cane, kenaf and groundnuts as major crops.
Table 9-2 shows that,of 8 crop-acres in 6 years, 6 crop-acres would be devoted
to the cash crops cotton, sugar cane, and kenaf and only 2 crop-acres to groundnuts
and beans. No staple food crop is included at all. The adoption of such a rotation
would involve the assumption that supplies of staple foods for the whole population
of the area could always be imported from elsewhere, at reasonable prices and with
sufficient certainty. Considering the location and circumstances of the projeot,
in a somewhat remote and semi-arid part of the country, this is quite unrealistic.
Few prospective cultivators would be attracted by an economy consisting essentially
of cash cropsj a man's first ooncern is to secure hie food supply, and it is essential
to grow sufficient basic foodstuffs every year, within the rotation.
The efficient production and handling of sugar cane calls for higly organized
plantation methods, rather than cultivation by individual tenants. Further, a
factory is essential, under skilled direction; to justify its heavy cost, there must
also be grown from the start a sufficiently large area of cane.
The cutting, retting, and processing of kenaf requires much labour which, for
efficiency, must be well organized, and even mechanized methods of decortication
need further development. As was brought out in the studies made, casual labour
does not exist in the area, nor is it likely to be easily attracted there in future,
unless it is well organized and continually employed, at fair rates.
It is considered that the whole question of the oropping plan to be adopted
requires more and very careful investigation, including trials and tests on a field
scale of varieties and yields of crops over a sufficient period to establish what
benefits may be expected. Such investigations are matters of some urgency.
Meantime, data are not yet available on which to make specific suggestions
as to potential cropping patterns which might be further considered. It does,
however, appear possible to envisage a pattern which omits sugar cane and kenaf,
but maintains cotton as the main cash crop, with groundnuts and maize or sorghums
as food crops. Cropping intensity would be slightly less than that envisaged in
the pattern originally suggested, but it might nevertheless provide a rate of net
farm revenue oomparable with the figure of E.A. Sh 950 per acre of holding, forecast
in Table 9-2 for the original cropping pattern.

-8-
2.5 Scheme of Development for Irrigation (See Chapters XI and XIIl) //
On the scheme of cropping originally contemplated, it was estimated that 1 cusec
of flow at Kordkora would suffice for an area ranging from 70 to 119 acres, according
to the month, the average over the year being 89 acres. On the basis of the 2,810
cusecs of firm flow expected to be ultimately available at Korokora, an area of about
250,000 acres could be irrigated. With releases from upstream reservations^and
some diversion of flows from the Athi river^this could, be increased to about 300,000
acres. The scheme of development for irrigation contemplated for these areas comprised
the following main works:—
(i) Korokora Diversion Dam and Reservoir. To divert flows of water from the
river at a level suitable to command the whole of the potential ultimate
irrigable areaj to provide some 196,000 acre-feet of storage capacity
to re-regulate the flows arriving so as to suit irrigation needsj and
incidentally, to provide some 600,000 acre-feet of dead storage, available
for sediment deposit sufficient to ensure the continued life and effectiveness
of the reservoir for a very long time,
(ii) Primary - Main Canal. To be aligned west of the irrigable area, which
would begin at Mile 38 from the head/
(iii) Secondary - Section Feeder Canals. To take off from the main canal at
suitable intervals.
(iv) Tertiary - Block Feeder Canals. To take water from (iii), through nightstorage
reservoirs, enabling irrigation to be given only by day. The canals
would deliver water to standard irrigation units, each of 50 acres,,
(v) Drainage System. Intended to deal with surface water from rainfall and
irrigation wastage,
(vi) Internal Road System. Envisaged as of various grades, but covering the
whole scheme. It was contemplated in the original studies that the more
important internal roads should be surfaced with stone. It is considered
however that this is so costly that it should be deferred until the
justification for it becomes clearly apparent. (See details on the following
page).
(vii) Land Clearing and Levelling for Irrigation. To include the preparation
of the necessary systems of channels for irrigation and drainage within
the 50-acre units.

- 9 -
The capital costs of these items may be summarized as follows:
Korokora Dam and Reservoir
For irrigation of 250,000 acres:
Irrigation and Drainage Works
Land Clearing and Levelling
Roads
TOTAL FOR 250.000 ACRES
For irrigation of an additional
50,000 acres:
Irrigation and Drainage Works
Land Clearing and Levelling
Roads
TOTAL FOR 300.000 ACRES
The equivalent overall rates per acre are:
With paved roads
With earth roads
Estimated
capital
cost with
paved roads
£ E.A.
11,040,000
20,698,000
7,283,000
14,070,000
£ E.A.
£ E.A.
2,720,000
1,457,000
2,855,000
Estimated
capital
cost with
internal
roads in
earth
£ E.A.
11,040,000
20,698,000
7,283,000
3,400,000
53,091,000 42,421,000
7.032.000
60,123,000
200 per acre
154 per acre
2.6 Infrastructure and. Secondary Developments (See Chapter XIV)
2,720,000
1,457,000
615,000
4.792.000
47,213,000
If 250,000 to 300,000 acres are developed, the agricultural population,
including families, would be between 400,000 and 500,000. Allowing for others
engaged in administration, processing plants and commercial enterprises, transport,
and so on, the total ultimate population might be from 500,000 to 600,000. Their
requirements would include housing and other buildings, water supplies, sewage systems,
power, and roads. In the studies made, the estimated following costs were forecast:
Townsite Development and
Services
Housing and Buildings
£ E.A. per head
90
110
£ E.A. 200

•10-
For a population of,say, 500,000 on an irrigation scheme of 250,000 net irrigable
acres, this is equivalent to £400 per net irrigable acre. Before this formidable
figure is accepted, all aspects of the basis on which it is assessed must be most
thoroughly scrutinised, including the method of sewage disposal contemplated.
Processing plants contemplated in the studies made covered the processing of
sugar cane, cotton, and kenaf. Details were not worked out, but the capital cost
for 250,000 acres was tentatively put at £ E.A. 40 million. This is equivalent
to £ E.A. 160 per net irrigable acre.
2.7 Organization and Management (See Chapter XV)
The region in which the scheme lies is remote and sparsely populated. To
attract settlers there, of prime importance will be the social and personal economic
faotors, including living conditions and amenities, marketing arrangements, conditions
of tenancy, and land tenure, and above all, the prospective financial returns to the
individual cultivator. To him, these will be of even greater importance than technical
agricultural factors, such as crops and yields, mechanized aids to cultivation,
and so on.
An adequate return on the high cost of development can only be possible with
high standards of husbandry and production. A proposal to set up a semi-autonomous
organization, to be called "Tana River Irrigation Authority" and to take charge of
the scheme, is important. Its funotions could include construction and operation,
marketing, research and training, with extension servioes, and secondary activities
such as forestry. For development, it would itself have to maintain a large construction
force, which might also undertake the provision of other public facilities - and
develop processing plants.
It must be stressed that the whole organization of the scheme, including cropping
patterns, conditions of tenancy and of cultivation, financial arrangements at all
levels from cultivator upwards, relationships between Government, operation and
management, need to be thought out and clearly defined, and agreed with all concerned
and then applied and tested on a first instalment of modest but adequate size.
2.8 Phasing of Development of Irrigation (See Chapters Xf XI, XII, and XIIl)
In the studies made, the expected rates of increase of demand for power indicated
that the reservoirs and power installations down to and including Mutonga might be
required by some date between I983 and 1993» and the full complex of installations by
some date between 1989 and 2000, according to the rate of growth assumed. Even the
amount of regulation of river flows to be provided by the reservoirs down to Mutonga
would suffice to ensure a supply of water for irrigation sufficient for the development
of 250,000 acres. According to the rates of development of irrigation assumed,
it was forecast that 250,000 acres might be developed at some date between 1989 and
2000, and this would correspond with the development of power foreseen.
These projections are fully reasonable on the assumptions made in the studies.
But, in view of the number and importance of the points requiring further investigation
and consideration — technical, economic, and social - it is considered that the
development to be contemplated in the near future should take the form of a first
instalment of 8,300 acres. The Research and Training Centre suggested in the studies
would be part of this instalment, but the primary aims would be production and
"in-service" training. Such an instalment would need at most about 100 cusecs of
water, and this would always be available from even the present minimum flow to be
expected in the river. The pumping installation and canal, contemplated for
the Researoh and Training Centre,would therefore suffice for the supply of the whole
instalment.

-11-
2.9 Economic Evaluation (See Chapter XVI)
Using the method of rate of internal return, with yields and values of crops
as discussed in the studies made, economic evaluations over a period of 50 years
showed the following, for ultimate areas of 250,000 acres and 300,000 acres, at the
minimum and maximum rates of development of irrigation.
Table 2-2 - Irrigation Development-Internal Rates of Return
Level and Rate
of Development
Irrigation development
only
Irrigation development
plus processing at 20
per cent return on
book value
Irrigation development
plus processing at 30
per cent return on
book value
250,000 acres
Rate 1 Rate 2
(Low) (High)
9.6
11.2
12.0
10.4
12.9
13.9
ftote: Period of analysis is 50 years and residual values are
300,000 acres
Rate 1 Rate 2
(Low) (High)
9.7
11.5
12.6
disregarded.
These figures relate only to the costs and benefits involved in the scheme
of irrigation itself. In considering them, however, regard must be given to all
expenditure involved, whether directly or merely indirectly in the development
contemplated. The capital costs of the various categories of such expenditure,
as forecast in the project studies, are summarised as follows:
Irrigation Development
Processing Plants
Housing, Town-sites, and Services
External Trunk Road (to Mombasa)
Irrigable Area - 250,000 acres
£ E.A. Million
53.0
40.0
100.0
8.5
10.6
13.1
14.1
£ E. A. /acre
212
160
400
34
201.5 806

- 12 -
Expenditure on this scale, though to be spaced over many years, calls for
the strictest and most thorough scrutiny before it can be accepted. This scrutiny
should include appraisal under four main aspects, viz:
(a) The standards of provision assumed, e.g. for housing, roads, etc.
(b) The designs and materials assumed, and the unit rates of cost expected.
(c) The production and benefits to be expected.
(d) The implications of the project, on the revised forecasts of costs
and benefits, not merely on its own merits, but also on comparison
with other projects, in order to assess the degree of priority which
each deserves, in the national interest.
2.10 Financial Analysis (See Chapter XVT)
The financial analysis dealing with one possible way of financing the
expenditure on irrigation development, makes the following conclusions:
(i) "if the Irrigation Authority was to be responsible for the development
of irrigation only, foreign financing would be possible on "soft"
terms, and on the assumption that domestic loans would be free of
interest."
(ii) "if the Authority were also to be responsible for processing, more
realistic foreign financing would become possible, provided the
Authority had full control of that financing."
It remains to be seen what financial analysis, and what conclusions, may
result from revised appraisals, following the further scrutiny and investigations
now recommended, in line with points (a) to (d) in (2.9) above.
2.11 Recovery of Costs from Cultivators (See Chaper XVI)
It was oonoluded that, in view of the conditions of the proposed development
and of its potential benefits to Kenya as a whole, an assured inoome for cultivators
should have priority in the financial arrangements over the meeting of charges on
the scheme, at any rate up to an income of £ E.A. 160/year/cultivator to begin with,
rising gradually to a maximum of £ E.A. 250/year/cultivator. Relief to cultivators
on the oost of housing was also suggested. This raises the question of the charges
to be made, and how they are to be assessed and oolleoted on individual cultivators -
whether on the amounts of water used, on areas of holding or of crops, or on values
of the actual amounts of crops grown. All these factors require careful consideration.

2.12 Size of Holdings (See Chapter IX)
-13-
Under the studies made, it was suggested that a 5-acre holding per family on
the proposed irrigation scheme, which would ultimately give the tenant £ 250 per annum
net, would fit conveniently into the irrigation layout, in which 50-acre units
would form the basic module of development. This may be convenient from an engineering
point of view, but it must be mentioned that such a rigid standard of ownership could
affect farm efficiency in the long run. There should be a certain degree of
flexibility in the size of holdings, which would help to provide incentives. All
that is required is to fix a minimum/maximum limit on the size of holding, say from
5 to 10 acres, depending on the size of family and the eagerness of the tenant
to operate the holding with greater efficiency.
2.13 Animal Husbandry
The contribution which livestock might make to the pattern of agricultural
output is shown in Table 9-2 to be only about 6 per cent per six-year rotation.
However, with the eventual development, of the lower Tana basin, the nomadic
character of the livestock industry would most likely give way to a more settled
form of animal husbandry. This in turn should increase the contribution of animal
husbandry to total farm output. It has been shown that fodder crops grow well
on the project area, and the possibility of dairy production should be fully investigated.
B. RECOMMENDATIONS
2.1 Need to Reappraise the Scheme for Irrigation Development
In view of the magnitude of investment required to implement an irrigation
development programme on the scale envisaged in the lower Tana river basin,
it is recommended that the Government review this scheme- in terms of Kenya's
general development strategy and priorities for investment.
2.2 Pilot Scheme
Due to the complexity of the proposed scheme, and the many technical, economic
and sociological factors which require consideration prior to its implementation,
the proposal to set up and develop a Research and Training Centre is fully endorsed.
Such a centre should however be primarily for production and in-service training of
all concerned. The Centre should form an integral part of a pilot scheme or of an
initial phase of irrigation development.

-14-
During the project, consideration was given to a number of locations for a
centre of this type. It is considered that an area of about 8,000 acres would be
necessary to provide for research and for a large demonstration training farm.
The latter could eventually be converted to normal tenancy holdings, with only a
part retained for continuing research and training activities. It is suggested
that the centre could be located immediately adjacent to the Tana river and south
of L.Hiraman, in an area representative of the major soil types of the project area
and centrally located in the northern region. It could then serve as the focus of
a community containing the Authority headquarters.
The pilot area could be supplied from a pumped water supply, as designed during
the project, the cost of which is estimated at £ B.A. 2,915,000.
The alternative proposal is to develop further the smaller scheme at Galole,
which has at present 1,200 acres under irrigation. It may be possible to extend this
for another 1000 acres or so to include a more representative proportion of soils
found in the project area. But, if it should be found feasible to proceed eventually
with a major irrigation development, the first area mentioned would appear to be
more suitable in the long term, as the central core of the project.
In the meantime, and until a final decision is taken on the location of the
permanent Research and Training Centre and the Headquarters of the irrigation
scheme, the agronomic research^ started during the; project and continued under Dutch
bilateral assistance since, should be consolidated. Under the original agreement
this aid was to terminate in March 19^9» but the Government has requested a three
years' extension. During this period it should be possible to gain sufficiently
reliable information ón crops, and varieties suitable for the area, and which give
adequate returns, for inclusion in a cropping pattern for application in the general
irrigation development of the project area.
2.3 Tana giver Irrigation Authority
It is strongly recommended that a Tana River Irrigation Authority be set
up as proposed, as being the only means to ensure the requisite standard of
efficiency. The whole organization of the proposed irrigation scheme, and
particularly the relations between the Government, the Authority and the cultivators,
should be thought out and agreed, and then tested in the first place on the pilot
scheme proposed. In this way adjustments can be made as necessary in the light of
experience, before full scale development is undertaken. It is also necessary to
ensure that close cooperation is maintained between the Tana River Irrigation
Authority and the existing Tana Steering Committee, which is responsible for the
execution of the hydroelectric projects in the upper Tana.
2.4 Further Studies
In addition to the reappraisal and further studies touched on above, a number
of specific points are mentioned hereunder for inclusion in the further programme
of investigation.
For example, studies should be made of the implications of the control of flows
for power, and the abstraction of water for irrigation, on the conditions of the
river channel downstream of the offtake at Korokora, in the event of a catastrophically
high flood. Observations should continue of climatic conditions, river levels and
discharges, rates of runoff evaporation and river losses, at all points relevant
to the development of the Tana basin, both for power and for irrigation. Observations

-15-
and analyses of the results should continue of sediment loads in the flows of the
Tana river, at suitable intervals of time, and at all significant points on the
river as far down as Korokora.
Detailed soil survey and land classifications should be made of all areas
contemplated for irrigation development as soon as possible and certainly before
detailed planning is undertaken. The effects and implications of the soils of the
lower Tana plains should be fully examined, particularly in respect of groundwater
conditions, and salinity risks.
The sociological implications of irrigation development on a large scale should
be fully examined, particularly as to the resettlement of highland people in the remote
and arid Tana lowlands and also the effects on the local riverine people of the lower
Tana.
2,5 Subsequent Action.
The Government of Kenya should consider how far the further action required in
connection with the project can be undertaken by its own departments and agencies,
and then in what manner and to what extent the Government may wish to seek for
external help to carry out the remainder of the work involved.

3.1 The Country
- 16 -
THE COUNTRY AND THE PROJECT AREA
CHAPTER III
The Republic of Kenya lies astride the Equator and stretches inland from the
Indian Ocean to Lake Victoria, encompassing a total area of 225,000 square miles.
Despite its location, a wide variety of climatic conditions are found within its
borders, due principally to the existence of prominent topographical features.
Along the 250 miles of coastline lies a narrow, mainly fertile, tropical belt,
behind which stretches a vast area of semi- arid desert, reaching to and beyond
the borders with Somalia, the Sudan and Ethiopia. Within the central high-lands,
the climate and vegetation change with increasing altitude from subtropical to
temperate.
Nearly three quarters of the entire country receives less than 20 inches of
rainfall annually, whilst only some 15 percent receives more than 30 inches.
Apart from the narrow coastal strip, the only areas of Kenya receiving enough
rainfall to support non-irrigated agriculture are centres around the Kenya massif,
in the Kisii Hills, and throughout the Mau escarpment and Mount ELgon areas of
western Kenya.
The peoples of Kenya, apart from the recent immigrants, belong to four of
the linguistically defined racial groups of Africa. It is not always easy to
identify a group in Kenya, since its members are not confined to distinct geographic
regions. The Bantu group is most numerous, comprising almost two-thirds of the
people of Kenya, and, though they speak many dialects, they can understand each
other. They include the Kikuyu and kindred tribes of the plateau, the Baluhya,
Kisii and Nyanza, and a number of coastal tribes, some of which have intermarried
with Arabs.
The second group, the Nilotic Jalue of the Lake Victoria shore, is more
homogeneous and comprises many tribal units that are bound together by very close
kinship affiliations. The Nile-Hamitic group is more difficult to define. These
peoples are spread throughout the country; the Masai in the south, the Nandi and
Kipsigis in the highlands above Lake Victoria, and the Turkana in the northwest.
All traditionally pastoral, they have no common language and differ in their
adaptability to sedentary agriculture. The remaining group is composed of the
nomadic Hamitic tribes of the northern provinces, distinctive from the other
African peoples of Kenya, being Caucasian in origin and Muslin by faith.

- 17 -
Growth of the economy of Kenya for many years has "been largely dependent
upon the intensification and extension of agriculture. Figures for the latter
part of the 1950's and the early part of the I960's indicate that about 40 percent
of the gross domestic product was derived from agriculture. It has been estimated
that more than 85 percent of the African population is employed on the land.
The import/export situation reflects, to an even greater extent the heavy
dependence on agriculture of the economy of the country. Imports into Kenya .
consist almost entirely of manufactured goods for industry, transportation and
agriculture, which the country is at present unable to produce. In the export
field, the earnings of agriculture, including livestock, have constituted over 85
percent of total earnings in recent years. The wide range of agricultural cash
crops produced in Kenya has compensated for the paucity of known mineral resources
and, at the same time, has protected the country from the effects of sudden changes
in the world market for particular commodities.
Prom I95O to i960, the total value of exported commodities more than doubled
and reached £35 million annually. In the agricultural sector, coffee has always
figured prominently in Kenya's exports, providing about,30 percent of total earnings
in I96IJ sisal.and tea each provided about 13 percent and pyrethrum 9 percent, while,
in the livestock sector, meat, hides and skins provided 10 percent.
The market price of coffee has been gradually falling over the past few years,
and the crop has consequently accounted for a smaller portion of Kenya's total
export earnings. Recent study of soils and land use in the highlands of western
Kenya has indicated a great potential for growing rain-fed tea, and the rising
demand for this crop on world markets appears likely to boost its export value
considerably in the future. Sisal has, in the past, occupied a significant place
in the export picture, but,, in recent years, due to widely fluctuating prices, the
crop has occasionally not been worth cutting.
The prospects for significant expansion of agriculture depend very largely
upon the availability of water supplies for irrigation.
There are few perennial rivers in Kenya and only two, the Tana and the Athi/
Galana, reach the Indian Ocean throughout the year. The wet side of thé country
in ITyanza, which forms part of the Lake Victoria catchment, has several perennial
streams. Por the major part of the country east of the central mountain massif,
however, the Tana river, which is the largest in the country, offers by far the
greatest potential of water for irrigation.
3.2 The Project Area
The Tana river basin encompasses a total catchment area of some 40,000 square
miles. The headwaters rise along the eastern slopes of the Aberdare Range and the
southern half of the Mount Kenya/Nyambeni massif, draining in a generally southerly
direction. Below these mountain regions, the central portion of the basin is a
plateau, gradually descending in steps to the eastern limit of the Basement rock
system, which lies approximately along a line joining the Koreh hills and the Kitui
escarpment. Between this rock system and the Indian Ocean, the river traverses a
vast peneplain, extending to the north and south beyond the limits of ill-defined
watersheds.

Physiography
-18-
On Plate 1, the entire watershed and its perennially contributing oatchment
are demarcated. A longitudinal axis, trending northwest-southeast through
the basin from Kipini at the coast to the upper catchment boundary near Nyeri,
measures some 300 miles, the mid-basin width on an axis through Garissa
measures about 180 miles.
The catchment is conveniently discussed in relation to the upper, middle and
lower reaches of the river. Por purposes of this report, the upper catchment is
considered as the area tributary to the main stream above the Kamburü suspension
bridge. This is in accord with past convention.
The middle Tana has previously been considered as that part of the basin
tributary to the main stream between the Kamburu and Garissa bridges. However,
geologic and physiographic considerations indicate that the middle Tana should
end at the Hargasso Falls, the last visible outcrop of the Basement rock system
along the main river. Thereafter, the Tana enters the sediments of the lowland
plains. In this report, this latter point has been adopted for demarcation
between the middle and lower catchments.
upper catchment tributaries drain much of the central highlands, a zone of
high rainfall. With the exception of a few deeply-incised stream valleys, this
part of the catchment lies above 3>000 feet elevation. The basin boundary passes
along the crest of the Aberdare Range, which rises generally to 10,000 feet, with
Mount Kinangop, elevation 12,816 feet, in the south and 01 Doinyo Lesatima, elevation
13>104 feet, in the north as the highest points of the range. Mount Kenya
rises to 17)058 feet and the divide places a little more than the southern half
of this mountain within the Tana basin. Above 15,000 feet, permanent snowfields
and glaoiers are found. The Kyambeni Range rises generally to 6,000 feet, with
Mount Itani, elevation 8,244 feet, in the west and Mount Ntoyer, elevation 6,466
feet, in the east as the highest features. The intermontane plateau of the upper
catchment slopes gently downwards to the southeast so that the surface elevation
decreases from near 6,000 feet at Hyeri to about 4>000 feet at the edge of the
Kitui escarpment.
The middle catchment comprises land lying generally above 1,000 feet elevation.
Part of the Mount Kenya Range, the southern slopes of the Nyambeni Range
and the northern part of the Kitui escarpment all lie within this portion of the
basin.
The lower catchment derives only intermittent runoff from an area lying
almost entirely below 3>000 feet; the major part is semi-arid desert lowlands
below 1,000 feet elevation.

Drainage System and Vater Resources
-20-
The upper catohment is drained by a multitude of streams descending the
slopes of Mount Kenya and the Aberdares in a series of precipitous gorges.
Gradually, these streams coalesce on the intermontane plateau. In the vicinity
of Fort Hall, the Maragwa and Sagana join to form the upper part of the Tana river
proper. Thence, the Tana flows first east to Kamburu, then gradually northward
around the foothills of Mount Kenya and the Uyambeni Range. At its confluence
with the Bisinadi, the river reaches the limit of its northward swing, about two
to three miles south of the equator. Between Fort Hall, and Kóreh Wells, the river
is augmented by many tributaries draining the southern flanks of Mount Kenya and
the Nyambeni Range« Among these are the Thiha, Thura, Ena, Mutonga, Kazita,
Thangatha, Ura, Rojewero and Bisinadi. The only significant tributary to join
the Tana from the south is the Thika river, which enters the main Tana hear its
upper limit. From the limited information available, it is believed that none
of the tributaries to the middle Tana downstream from the Rojewero flow perennially.
Downstream from the Bisinadi, the Tana trends gradually more southerly until
from Oarissa it flows a few degrees east of south on its final course to the Indian
Ocean. In the vicinity of. Koreh Veils, the river emerges from the foothills and,
thereafter, flows in a tortuous meander pattern, crossing and recrossing its flood- .
plain, until its final debouchment into the sea at Kipini.
Plate 2 illustrates the precipitous character of the upper Tana and.its
tributaries, the series of abrupt descents as the river traverses the foothill
region, and the final gentle gradient across the desert plains to the sea.
About eighteen percent of the catchment area lies above 3,000 feet,.while
forty-five percent lies below 1,000 feet. It is significant to note that the
total area contributing to perennial runoff comprises some sixteen peroent of the
basin. This coincidence with the area of the basin lying above 3,000 feet
indicates the olose relationship between topography and rainfall.
The long-term water yield of the catchment at points on the Tana river and the
inflow from important tributaries are given in Table 3-1» I* may be noted that
the long-term average flow increases throughout the length of the middle catchment.
Thereafter, from the point at whioh it enters the Hameye swamp at the head of its
lower reaches, the river suffers a net loss of water.

liOt 11JHS U2-VS-HOI-H

• J*0 I 13»* UI-V«-MOI -•*

- 23 -
Table 3-1 - Long-term Average Flow - Tana River and Tributaries
Tana River Tributaries Catchment Estimated
area long-term
average
flow
square miles cusecs
Thiba R. 815
Kamburu
Ena, and
minor streams
Mutonga
3,500 3,125
535
1,060
Grand Falls
Koreh
Kazita
Thangatha
Ure
Rojewero
Bieinadi,
and minor
6,800
9,500
410
5,130
75
120
160
95
5,580
Garissa
12,500 4,750
Climate
•
The climate of East Africa is controlled by the northward and southward
movement of the sun, which creates a zone of low pressure at the latitude of
greatest heating. This zone is referred to variously as the Heat Trough,
Equatorial Trough, or Intertropical Convergence Zone* Climate occurrences
have generally been shown to lag behind the movement of the Trough by four
to six weeks* The sun is directly overhead in March and in September« one
rainy season occurs in late April and lasts through May} the other occurs in
late October and lasts through November, (l)* Between the monsoon-type rainy
seasons, the climate of the country is generally dry} with a cool "winter"
through June and August and a hot "summer" from January to late April. However,
these terms are only relative, since mean monthly temperatures in East Africa
show quite small seasonal changes, the variability being much more closely
related to altitude*
Rainfall is undoubtedly the most important climatic factor in East Africa,
and thus the climates of the various regions of the Tana basin are largely
defined by their rainfall regimen. Permanent agriculture is limited to those
areas receiving 30 inches or more of reliable rainfall annually} semi-permanent
and shifting cultivation is practised in the marginal zones receiving 20 to 30
* The numbers in brackets in this Chapter and throughout the report refer
to the works listed in Appendix 17 (References).

- 24
inches of reliable rainfall, and the under 20-inch.rainfall zone is managed
largely as rangeland. As Plate 3 shows, most of the Tana basin receives less
than 30 inches of reliable rain annually and more than half the basin would be
classified as semi-arid, with average annual precipitation' varying from 10 to
20 inches (2)*
Vegetation
The vegetation across the basin ranges from lush tropical growth along the
narrow ooastal strip, to afro-alpine heat and moorland, high mountain forest and
grassland, on the upper slopes of Mount Kenya and the Aberdares. Between these
extremities are the vast areas of savannah and acacia forests of the upland
plateau, and the open" woodlands of low thorny species - dormant for most of the
year - which cover the lowland plains.
Population and Peoples
Population density in the basin varies widely. Some areas in the upper and
middle catohment plateau and foothills, occupied by a group of Bantu peoples
comprising the Kikuyu, Qnbu, Meru and Mkamba tribes, have more than 600 persons
per square mile. The desert lowlands in the lower basin, inhabited by several
tribes of Hamitic origin (the Orma, Galla, Boran and Somali peoples) which are
nomadio by tradition, have average densities of less than two persons per square
mile. In the narrow riverine plains of the Tana, between the Eameye swamp and
the Indian Ocean, live the Pokomo, another Bantu tribe. In the coastal strip
are found the Giriama, Swahili and Arabic peoples (2).
Communications
Road systems are well developed throughout most of the populated areas of
the upper basin, but, with the exception of the Nairobi-Thika-Nanyuki road,
surfaces are unpaved. Many of these roads are impassable from time to time
during the rainy season. The middle and lower parts of the basin are served by
only a few earthen roads, impassable during the wet seasons. The chief of these
are the Nairobi-Garissa road and the Garissa-Mombasa road, which passes through
the proposed irrigation area, Galole, Garsen and Malindi. There are only two
permanent bridges across the middle and lower Tana5 the first, at Kamburu, links
the Kitui and Qnbu areas, and the second, at Garissa, gives access to the
sparsely populated northeast desert region. The hand-operated car ferry at
Garsen is used during low and medium river stages and links the north coastal
area with the south coast of Kenya.
The main rail line between Mombasa and Nairobi passes to the southwest of
the basin and serves the lower area only from these principal termini.

- 26 -
The upper basin is crossed by a branch line from Nairobi, which goes through
Fort Ball and Nyeri to Nanyuki. Air communication is important, particularly
to the lover basin, which, during the rainy season, is frequently isolated from
the rest of the country. Garsen, Galole and Garissa have landing strips and
services by light planes from Nairobi, Malindi and Mombasa - centres which are
interconnected by regularly scheduled internal airline service.
Geology, Seismology and Mineral Deposits
Plate 4 shows the relationship of the Tana basin to the regional geology of
eastern Kenya. The Basement System underlying the entire central massif of Kenya
consists of folded Precambrian metamorphic rocks. These are overlaid in the west
by younger volcanic rocks of Tertiary to Quaternary ages and in the east by
sedimentary rocks of Carboniferous or Permean to Tertiary age and semiconsolidated
sediments ranging in age from Tertiary to Recent,
The entire area east of the Gregory Rift was reduced to a peneplain, and
parts of the final Submiocene level are identifiable along the Kitui escarpment
and elsewhere (3). Subsequent volcanic aotivity resulted in the build up of
the Aberdares, Mount Kenya, the Nyambenis, Mount Kilimanjaro, and the surrounding
upland region of Kenya. Farther east, downwarping of the peneplain was caused
by deposition of later Tertiary and Quaternary sediments in an area referred to
as the Tana Embayment.
The higher-lying Old Alluvial part of the lower Tana basin, within which
lies the major portion of the project lands, represents a Pleistocene erosion
surface whereas the lower-lying floodplain of the Tana river is considered to be
Eolocene valley fill, at least insofar as its upper soil layers are concerned.
At the present time, the lower reaches of the riverlare incised within its own
recent sediments.
In common with the rest of East Africa, Kenya has suffered from earthquakes
related to fault movements and volcanic activity. Almost invariably, the epicentres
of earthquakes have been in the western part of the country, in the area
of the Rift fault and its volcanoes. East of the Gregory Rift, in the area of
Precambrian rock and farther east in the younger sedimentary areas, there is
little danger from earthquakes. Nevertheless, shocks have been felt as far east
as Mombasa and Malindi. Farther inland, perceptible tremors have been reported
from Voi on the Mombasa-Nairobi road and in the north near Marsabit.
No significant mineral deposits are known to exist in the middle and lower
catchments of the Tana river, with the exception of gypsum, which has been
identified at a number of locations west of Garissa. This, on test, has proven
to be of low quality, although possibly suited to agricultural purposes.

ir
LEGEND
WVJ PL00O PLAia OCPOaiTS \ BAND, »ILT,CLAV)
XXXM ADD MAaOAUU. aWAItP OIPOSIT» («ILT.CLATl
|'::-.'..'-l MDtMNTS I OaAVKl .SAMO.aiLT.CLAV, URL t
1^ [ : . 1 LOCALLY CMtHTEO
1.»" 3 ÏOLCAKIC »ocm
IV.V1 «0>TLT •«»«LI L«V« PlO«*
P'"M BIOIMCNTART poena
Z'.'.'/A MOtTLT tAHOtTOMt AHO LltttSTOM
I I POLOID NOCK«
1 | intTLT miCAMtuii «IIA«O»»«IC Aa» laacout
r~—"n laüIOU« IMTftuttVC aOCKa
1 «^ 1 «OttLt «»IIITM, ITUITII , «AiMO»
SYMBOLS
« » M » PAULTP - PNOaABLt
NOTE
QIOLOOICAl. OOUHOAaif» AKI A»MOKI«ATf.
•ut* OP toni atOLOaiCAL PIATUM» AAI
IIAaOMATID
SOURCES OF DATA
I matt >M aioioar UNITIHT
t-wATi« oivtiopviiT atrAaratat
lauavcT OP RCMVA . »mooi
• •.p.- aaiiL pfToóLiua at»tLom«»T
COUPANT op •••TA imiTie, ••••AOA
• CALt 1 > »,OOOAOO
1CALI 0 40 M «LOMTCU
' »CALI 0 40 to mua
80VERNMENT OF KENYA
UNITEO NATIONS SPECIAL FUND
SURVEY OF IRRIGATION POTENTIAL
LOWER TANA RIVER BASIN
FOOO A» aanCULTUK OMUIl«'*» Of THE UMTEO MTMS
EASTERN KENYA
GENERAL GEOLOGY
ILWCO /ACRES -
PLATE 4
I

Irrigation Projeot Area
- 28 -
Early reconnaissance of the lower Tana basin below Saka quickly oonfined
the area of investigation to the right bank óf the river between Bura and Valu,
where soils and topography in combination afford the best prospeots for gravity
irrigation. Modifications to the investigatory limits were later established from
considerations of possible diversion sites for gravity development and resulted
in the adoption of the project area illustrated on Plate 1.
This area is traversed from west to east by a number of dry "luggas", or
streambeds, which from time to time are subject to wild flooding. The most
important of these is the Thowa Galole, which drains part of the Eitui escarpment.
This physical barrier has been adopted as a natural boundary dividing the irrigation
projeot area into northern and southern divisions.
Present Development
In the upper catchment, the intermontane plateau has been intensively
developed for agricultural use. Such orops as tea, coffee, pyrethrum and sieal,
which are extensively grown on estates, are sensitive to mesoclimatio differences
and therefore thrive at varying altitudes. Part of the upland foothills are
utilized for large-scale mixed farming and ranohing, but most of the land is
cultivated by Africans growing a variety of subsistence crops. The rugged upper
slopes of the Aberdares and Mount Kenya are heavily forested and provide a variety
of tropical hardwoods. As wildlife abounds throughout the uplands, tourism is
important in this area, and such internationally known attractions as Treetops
and the Mount Kenya Safari Club are located near the upper catchment divide.
As rainfall gradually diminishes towards the Kitui escarpment, cultivation
becomes less extensive and completely subsistence-oriented. Throughout the arid
lowlands, the nomadic peoples pursue a pastoral existence in which cattle, sheep
and goats become the index of wealth and the medium of exohange. The riverine
Pokomo are principally cultivators who subsist on crops, the yield of which is
dependent to a large extent on the vagaries of the twioe-yearly flood. However,
their diet is augmented by fishing along the Tana, where eels a few migratory
species such as barbus and labeo can be caught (4;.
A small pre-investment irrigation scheme begun at Galole in 1955 at present
comprises some 1,200 acres of land. Irrigation water is supplied from a
floating pump station located about twelve miles upstream at Makere.
The floodplain of the Tana gradually widens from Garissa downstream, and
enters a tidal delta below Oarsen. Immediately adjacent to the coastaline, a
small area has been planted with coconut and other tropical tree fruits.

Potential Development
- 29 -
The Tana river is the largest perennial river in Kenya and its water and
land resources offer the greatest potentials for hydroeleotrio power generation
and irrigated agriculture within Kenya« The power potential of the middle
reaches of the river is estimated to he some 6*00 megawatts, while irrigation for
continuous cropping of 230,000 to 300,000 acres per year in the lower hasin is
technically feasible. Even with full exploitation of the power and irrigation
potential,however, most of the middle and lower parts of the hasin will remain
virtually undeveloped.
To the extent that controlled range management praotices can he introduced,
some improvement in the livelihood of the pastoral peoples outside of the irrigation
project area may he expected. In economic terms, this improvement would he
modest, hut nevertheless, significant, With the opening up of communications
and the provision of a market for the nomadic peoples, it is expected that the
proposed irrigation development will reflect some secondary henefit throughout
the lower hasin and surrounding regions of the northern frontier area. The
economic and social significance of this likelihood are discussed later in this
report.
The development of irrigation will require storage of water in a number of
reservoirs which, it is believed, can be used to establish a substantial inland
fishery. Such fisheries will offer further inducement to populate the desert
area and increase the benefits from primary development.
The coastal area of the basin is being considered by others and forms no
part of this study. It may, however, be remarked that, so far as is known, the
potential of this region is quite restricted. Partial control of flooding and
reduction of long-term flow reaching the delta region of the Tana as a result
of the irrigation project may enable reclamation of parts of this area to be
considered. Certainly, within the limits of locally adequate rainfall, future
planners should not overlook this area.

- 30 -
METEOROLOGY ABI) HYDROLOGY
CHAPTER IV
As there are deficiencies and anomalies in the records of basic data for
much of the catchment are under consideration, prudence has suggested a conservative
approach to water yield evaluations throughout all phases of the studies.
Consequently, it is quite possible that the development potential which could
ultimately be realized would be somewhat greater than is estimated in this report.
In that case, power developments in the middle reaches of the river and irrigation
development on the lower rightf^bank plains would more economic. From considerations
of the value of even modest increases in water availability, as illustrated by the
discussion on the value of water in Chapter XII, it is reasonable to ezpeot that
future reappraisals based upon more complete hydrologie data will tend to be more,
rather than less, favourable to development.
To provide the design parametres on which the studies of the engineering and
agricultural layouts have been based, hydrometeorologic analyses have been undertaken
and are discussed in Section 4»2 following. Greater detail relating to
these studies is to be found in Technical Report Vol.11 - Appendix A - Hydrology
and Meteorology.
4.1 Hydrometeorologic Data
The climate of the basin is distinguished by two periods of rainfall and two
periods of drought each year. The rainfall gives rise to semi-annual flood
periods. Occasionally the rains fall and one or other of the flood periods does
not occur} or, alternatively, as happened in Ootober/November, 1961, prolonged
heavy rains result in floods of damaging magnitude. These characteristics,
together with the normal month-to-month variation in the flow of the Tana
(illustrated on Plate 5), lead to the need for storage to oontrol the natural
river flow and provide for release of water in a sequence more benefioial to
power and irrigation development.

-, _L_j__ — i
too
1
1
f 1
'IÜU
Jjlüü
h
!"
r
.
[.. _.. -- •
-
1
t
i
i
1
1
1
1
• - ' • • - — — - •
. Ï«Ï'J
THC DATA INDICATED OH TMC PLATE
WAS OBTAINED AS FOLLOWS '•
IMT-H4T rnrrwMis mm * NUMTALL
1 «MOFr OWWLITKW
— — \
r ._.
1
1
i
»00
l
I
II4T - IMI FMOH NECOWM WW BV TMC
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NMW - IMZ CSTtMATCO fLOOO M W T
tv F. (wuNOv («trtKK* >
!
!
1 Il i NOTE
1
M j i 1 i «••€» CATCHMENT AU.OCATKMS MM«
. 1
NOT «CC* DfOUCT»
1
Hl
A i i
\ , 1 e ƒ l/l y I \ i
A L \ \ i l/i / i J 1 r II V Jv L AOVUNMIHT of klhV- * — '
1/ UIITIO NaT «Ht irCCIAL FtMO
h*1 -h H V ƒ
I \ i
T-i L \ \ i / i J I \ i
V Jv SURVEY OF IRRIGATION MTCNTIAL
LOWER TANA RIVER iÀilN
\ V l
l( JH \ V 1
I \ i
SURVEY OF IRRIGATION MTCNTIAL
LOWER TANA RIVER iÀilN
T-i
\ V V l( JH l y ' V ü J
\ V 1
I \ i
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FOOD MO MRcaniK mmuHM or t« «ami MTMW
y ' V ü J ' I ' H 1 ^ iV
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y ' V ü J HYDROGRAPH OF AVERAGE
m i i , 1 1 l H | -ht
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'MT 1U it» '»«0 '»«« '•«* '*«ï «1«« j '»«5 , >'*•* '*•' ! "•• 194»
""
i»it t«i IM1 l«4 193» 1*31 IMT ItSI l»9t IttO • »ei l*IS
MONTHLY DISCHARGES
TANA RIVER AT KAMBURU
^iftM^Sr^
PLATE 0

- 32 -
In East Africa, meteorology is the responsibility of the East African Meteorological
Organization and hydrology is the responsibility of the Vater Department
in Kenya, Uganda and Tanzania» At present no formal means exists of co-ordinating
meteorologie and hydrologie investigations in water resources studies for agricultural
and engineering purposes, and the formation within Kenya of a co-ordinating
organization, charged with responsibility for planning the instrumentation and
operation of hydrometeorologic networks in major river basins, would assist in
avoiding both repetitions and omissions in the gathering of information.
It may be noted that, as a part of the field investigations for this study,
the establishment of a basio network of hydrologio stations covering the main stem
and important tributaries of the middle and lower river was undertaken» Hydrometeorologic
stations, including those established during the current studies, are
shown on Plate 3.
Heteorologio information for agricultural purposes in the lover Tana has been
supplemented under the project by establishing comprehensively instrumented "Penman"
stations at Galole and Kayu. Bain gauges and other meteorological equipment have
also been provided to augment the existing network wherever it is possibile to
arrange for reliable operation» Although few stations have, so far, been added to
the basic rain gauge network, the aim has been to obtain more representative coverage
of the middle and lower catchments» But the scarcity of population in these areas
limits the establishment of operations to a considerable extent.
The operation of these new hydrometeorologio stations has been organized under
the direction of the Water Development Department. It is hoped that conscientious
gathering of data will continue and thereby provide the reliable records necessary
to confirm the estimates presented in the report and to facilitate revisions, as
justified, at the design stages of development.
4»2 Hydrometeorologio Analyses
Water Availability
A study of the mean rainfall in the upper oatohment, based on selected stations
which have been operated almost continuously since 1917* indicated that the period
1947 to 1963 for whioh discharge records are available at Kamburu, was wet in
relation to the average since 1917* Therefore, so as not to place undue emphasis
on a wet cyole in the estimation of irrigation and power potentials, it was necessary
to extrapolate the runoff record backwards in time to cover a more representative
period.
Studies indicate that the 25-year period from March 1937 to February 1962 yields
the same long-term rainfall average as the longer period 1917 to I964 and, further,
contains several periods between 1933 and 1950 likely to have been the driest in
this century and consequently the most oritioal for the study of storage requirements.
Correlations of runoff at Kamburu and Grand Falls with appropriate rainfall
indices yielded mean values within one percent and mean errors within the probable
limits of accuracy of the observed data. These correlations were then used to
synthesize the discharge record for the period between 1937 to 1947 to 1948.

-33-
The synthetic and real data for gauging stations were then adjusted to take
account of water already allocated for future demands in the upper catchment) and thus
to estimate the .long-term availability of water at the damsites under consideration
(see Chapter Hi). -Allowanoe for potential upper catchment demands, as reserved by
the Water Apportionment Board, amounting to 338)000 acre-feet annually, has been
considered in the.computation of net flow records. This volume,which is in addition
to those authorizations granted prior to September 1956*, and for which an allowance
of 44,000 acre-feet annually has been estimated, is in accordance with the revised
authorizations issued by the Chief Hydraulic Engineer, in'October 1964.
Latterly, it has been found, as discussed in Chapter XII,that the value of
water from the upper catohment to the proposed downstream power and irrigation
developments is sufficient to justify further review of the needs for these upstream
allocations. While no formal review has, aB yet, been made, informal disoussions
have been held with the appropriate Ministries. It is understood that the projected
upstream development upon whioh the present reservations were based is no longer
considered valid and that a substantial portion of the allocations may be released
for downstream uses« Based upon present usage and foreseeable commitments, this
may be up to 400 oubic feet per second»
Some indication is given, therefore, in Chapters XI, XII and XIII of the value
and additional development of power and irrigation whioh would accrue through
reduction of upstream allocation reserves by 284,000 acre-feet annually.
Adjustment of the flow records to represent discharges at the various damsites
under review in these chapters was undertaken from intermediate tributary flow records,
insofar as this vas possible, and from general considerations of rainfall distribution
where tributary data was inadequate. The estimated net monthly volumes contained in
Annex A-l in Technical Report Volume II are considered to be sufficiently reliable
for the present evaluation of the various projeots.
To indicate the magnitudes of these flows and their distribution over the year,
Table 4-1 gives the average figures for monthly and annual flows available at two
sites, Seven Forks (Confluence; and Koreh, over the years 1937 to 1962«
Seven Forks
(Confluence)
Koreh
Table 4-1 - Net Discharges at Seven Forks.(Confluence) and at Koreh
(thousands of acre-feet)
J F M A M J J A S 0 S D Tear
82
200
44
129
51
132
237
467
411
634
209
357
121
226
107
212
88
166
129
243
263
547
143
347
1,885
3,660

Table 4-^2 - Long-term Average Flov and Net Available Flov
Tana River and Tributaries
Tana river Tributaries Catchment
area
Kamburu
Grand Falls
Thiba H.
Ena, and
minor
streams
Mutonga
Kazita
Thangatha
Ure
Rojevero
Bisinadi,
and minor
streams
Estimated
long-term
average flov
square miles cuseos
815
3,500 3,125
535
1,060
410
6,800 5,130
75
120
160
95
Upper
catchment
allocations
ouseos
I65
Net available
long-term
average flov
ousecs
65O
530 2,595
530 4,600
Koreh 9,500 5,580 530 5,050
Garissa 12,500 4,750 530 4,220

-35-
It must be remembered that tbe totals for individual years have varied widely
from these mean totals - at Seven Forks ranging from 31 percent up to 288 percent
of the mean, and at Koreh from 40 percent up to 258 percent of the mean. In individual
months, the variations from the mean shown in this Table «ere even vider in
range. These faots show clearly the great need for annual regulation on a large
scale, as contemplated. For maximum use of available flows, some measure of over
year regulation also would be desirable, if found to be feasible. Review of the
estimated water yields should be made when longer periods of reliable reoords are
available. The long-term net average rates of flow at these and other selected
main-stem stations are presented in Table 4-2.
Flood Estimates
As a part of hydrologie study for storage development, it is necessary to make
the best possible estimate of potential flood discharge at the site, so that
adequate provision for the safe passage of such a flood past the dam can be made.
Modern oonoepts of "design flood" estimation involve consideration of both "maximum
probable" rainfall and the characteristics of the drainage area in transforming the
rainfall into flood runoff, unfortunately, for reasons discussed in Technical
Volume II (Appendix A), such an approach has not been possible for the damsites
under review, and statistical methods have had to be relied upon. These are,
however, quite reliable for present purposes.
For the protection of human life and property, and in the absence of more
refined estimates, it is essential to seleot a flood of rare frequency for spillway
design. In these studies, a return period of 10,000 years has been adopted, which
is equivalent to accepting a one percent ohanoe that the selected flood will occur
during a 100-year period. In Table 4-3» the one in 10,000-year flood-peak estimates
adopted for the various damsites under consideration are listed, together with the
I96I peak estimates, where available, for comparison.
Table 4-3 - Estimates of "Design Flood" Peak Discharge
Used in the Studies
Damsite 1 in 10,000-year peak Estimated 196I peak
cusecs cusecs
Seven Forks Reservoir 115,000 45,500
Seven Forks Confluence 150,000 .74,000
Kiarabere. 150,000 a
Mutonga 200,000
Grand Falls 250,000 138,000
Adamson's Falls 320,000
Koreh 350,000
Korokora 250,000 110,000

-36-
The East African Meteorological Department was requested to comment on the return
period of the rainfall causing the 1961 flood. A preliminary estimate of 100 years
has been received, which value is consistent with the computed frequency of this
flood.
Diversion of river discharges would be required during construction of any of
the dams considered hereinafter» In accordance with normal design practice, the one
in 20-year flood has been selected for the design of diversion works. In Table 4-4
the diversion flood peak discharges used in these studies are given.
Table 4-4 - Estimates of Diversion Hood Peak Discharges
Used in the Studies
Damsite Estimated Diversion Flood Peak
Discharges
cuseos
Seven Forks Reservoir 33,000
Seven Forks Confluenoe 42,500
Kiambere 44,000
Mutonga 57,000
Grand Falls 65,000
Adamson's Falls ~ 70,000
Koreh 75,000
Zorokora 70,000
Evaporation Estimates
Estimates are required of the average monthly potential evaporation at reservoir
sites, and of month by month évapotranspiration from cropped land within the irrigation
project area.
c
From the data available at eight meteorological stations, the relationship
between potential' evaporation and altitude has been established and provides rates
appropriate for reservoir sites. So as not to overestimate actual evaporation,
the average rainfall on the reservoir surface area, selected from the isohyets shown
on Plate 3, has been deducted from the potential rates to obtain the net values
listed in Table 4-5*
The meteorological data available for the stations at Oalole and latterly at Wayu
have been used for calculating Penman estimates of potential évapotranspiration
from crops in the project area. In Table 4-6 are listed the monthly average values
of the Penman estimate as used in these studies»

Damsite
-37-
Table 4-5 - Average Annual Evaporation and Rainfall Rates
Used in Evaluating Potential Storage Reservoirs
Average
annual total
evaporation
Average annual'
incident
rainfall
. Net evaporation
rate on reservoir
surface area
inches inches inches
Seven Porks 86 29 57
Mutongaj Grand Falls 97 26 71
Adanson's Falls 100 - 18 82
Koren 101 H 90
Korokora 103 12 91
Table 4-6 - Monthly Estimates of Potential Evapotranspiration
for the Pro.ject Area
Potential mean
Month evapo transpir ation
feet
January 0.66
February 0.60
March 0.65
April 0.60
May 0.62
June 0.56
July 0.55
August 0.59
September 0.61
October 0.63
November 0.61
December 0.64
Annual total 7.32

Rainfall - Project Area
-38-
The analysis of rainfalls in the projeot area falls into two parts; first the
determinations of monthly rainfall reliability« so that justifiable reductions in
the volume of irrigated water required can be allowed; and secondly) the estimations
of storm rainfalls* so that drainage facilities within the agricultural lands can
be designed*
Plate 3 shows that the irrigation project area lies generally between the 10-inch
and 20-inch average annual isohyets. Average annual total precipitations of 18 inches
at Galole and 20 inches at ffayu, in comparison with 12 inches at Garissa, suggest
that the southern portion of the area is wetter . than the northern part. However«
the presently available data is not sufficiently detailed to justify any attempt at
computing variations in rainfall reliability across the projeot area.
The total rainfall« however, is less significant than that portion which can be
considered reliable in conserving irrigation applications. Monthly recurrence
intervals of effective rainfall for both Garissa and Galole were determined, and the
results for the Galole station are presented in Table 4-7«
Table 4-7 - Monthly Récurrence Intervals of
Effective Rainfall at Galole
Probability
Effeotive rainfall
of
inches
exceedance Jan. Mar. Apr. May Oct. Nov. Dec.
2 yrs in 10
4 yrs in 10
6 yrs in 10
8 yrs in 10
1.25
0.10
1.07
0.04
1.80
0.90
0.40
0.70 1.61
N.B. For the months not listed, the probability of reoeiving significant effective
rainfall is negligible.
Confidence limits of effective rainfall reliability were computed for the Galole
data. The results of this study indicate that significant effeotive rainfall can be
relied upon only during the months of April. November and December.
The most severe - rainfall recorded in the irrigation projeot area occurred from
September 26 to 28, during the early stages of the 1961 flood period, when a total
of 7*13 inches was recorded at Galole and 4*40 inches at Vayu. Apart from this
incident, most of the falls over two inches have occurred during the months of April,
November and December. Table 4-8 lists the maximum rainfall expectation in the
project area for various recurrence intervals. A maximum daily rate of 2.05 inches,
to be expected once every three years« was selected for the preliminary design of
project area drainage channels«
0.17
3.40
1.80
0.80
1.60
1.10
0.80
0.35

Recurrence interval
Annually
1 'year in 2
1 year in 3
1 year in 5
1 year in 10
Sediment transport estimates
-39-
Table 4-8 - Recurrence Intervals of Maxi mi m Rainfall
in the Project Area
Rainfäll total
inches
1 day 2 day 3 day 5 day
The upper tributaries of the Tana river drain regions of deeply dissected, ridgeand-valley
topography« where considerable areas have been cleared for agriculture.
In other parts of the catchment« overgrazing is common. The incidenoe of heavy
rainfall on such unprotected soil results in transport of large quantities of topsoil
into the streams and rivers in the form of suspended sediment. As agricultural
development in the upland areas proceeds, clearing of still larger areas without
adequate soil conservation measures could result in aggravation of this problem.
The application of soil conservation measures is therefore necessary to ensure
that soil erosion in the future at least does not exceed present levels. Otherwise*
higher sediment concentrations in the river would have an adverse effect on the
storage function of any reservoirs that are developed.
Estimates of annual sediment transportation have been made for each of the potential
storage developments by combining sediment concentration data with flow duration
analyses to provide time-weighted averages, as shown in Table 4-9 below.
In computing the estimates in Table 4-9 f° r downstream sites, it was assumed
that the Seven Forks complex would have heen developed previously. However, it is of
interest to note that concentrations of sediment below Seven Forks are substantially
greater than those above, thereby indicating that the major areas of soil erosion are
the eastern slopes of Mount Kenya and the Nyambeni Range. Development of a reservoir
at Seven Forks, therefore, will not significantly affect the quantities of sediment
that will be received at the lower sites. Estimates of sediment volumes retained in
downstream reservoirs, for those cases where control has already been provided at
upstream sites, are based on the assumption that a maximum of 55 percent of sediment
(the estimated "wash load") may be "vented" at each of the developments. A deadstorage
volume has, therefore, been included in the analysis of all reservoir sites
to allow for deposition of sediment.
1.05
1.65
2.05
2.50
3.20
1.85
2.55
2.95
3.30
4.50
2.20
2.90
3.40
4.00
4.80
3.00
3.80
4.30
5.00
8.60

- 40 -
Table 4-9 - Sedimentation Estimates at Potential
Storage Sites
Samsite Estimated
average
annual oost
Estimated volume
oooupied by sediment
after 50 years
million of tons thousands of acre-feet
• Seven Forks Reservoir 0.25 8
Seven Forks Confluence 0.35 11
Mutonga 7.00 220
Grand Falls (without'Mutonga) 12.00 375
Grand Falls (with Mutonga) 8.80 295
Adamson's Falls (with all
upstream plants developed) 9.60 350
Koreh (with all upstream
plants developed) 10.80 380
Korokora 23.00 720
Korokora (with Mutonga and Grand
Falls developed) 17.50 600
Korokora (with all upstream plante 1
developed) 1
I5.IO 525
A pertinent faotor in analyzing the effect of sedimentation on reservoir
design is the estimation of the location in the reservoir where the sediment
will settle. Particularly in the oase of the Koreh reservoir, and to a greater
extent at Korokora, the broad shallow configuration of the storage basins might
tend to result in much of the sediment settling near their upper ends, thereby
occupying space normally recognized as useful or "live" storage. This subject
will require further detailed study during design stages.

-41-
SURVEYS. GEOLOGY AMD ENGINEERING COST DATA
CHAPTERV
To facilitate evaluation of the development potential of the lower Tana basin,
various topographic, geologic and geotechnioal surveys and investigations have been
carried out. In addition, to provide the basis for estimates of capital and
recurrent costs of various developments considered, construction, maintenance and
operation charges for works undertaken in East Africa have been assessed.
5.1 Topographic Mapping
To provide the topographic data required for the various phases of the studies,
a number of special maps were.compiled by the Survey Department of Kenya, with the
assistance and co-operation of the Directorate of Overseas Surveys and the Survey
Section of the Water Development Department. The various map series prepared were:
(a) 1:100,000 scale. This special series of maps with 25-foot contours
was oompiled in advance of the survey of irrigation potential.
Coverage was provided of the lower river basin between Saka and Garsen.
(b) 1:50,000 scale. Two series of 1:50,000 maps were prepared for this
study. The first comprised coverage of the irrigation project lands
north of Thowa Galole and shows 5-foot contours. The second, which forms
part of the national 1:50,000 topographio series, was prepared to provide
coverage of the main river valley between Seven Forks and Saka. Contours
at 25-foot intervals up to approximately 300 feet above river level were
interpreted from aerial photography and ground control surveys»
(c) 1:10,000 scale. Mapping of an area of 10,000 acres, within which the
proposed Permanent Research and Training Centre is to be located, was
prepared with 2.5-foot contours interpreted from detailed ground control
surveys.

-42-
(d) Other. Topographic maps of potential damsites at various soales suitable
for preliminary design layout studies.
5.2 Geologic Surveys
Geologic investigations were oarried out to assess foundation conditions at
the proposed Korokora diversion dam and at upstream power and storage sites. In
addition, investigations were made of the main canal alignment between Korokora
and the projeot area, of gypsum deposits which may be needed for treatment of
irrigated soils, and to locate suitable sources of rook material for road metal,
concrete, riprap and other construction purposes.
The following sections summarize the general geology, seismology and economio
geology of Kenya, with particular reference to eastern Kenya, wherein the Tana basin
lies. Thereafter will be found brief seotions discussing the specifio geologic
investigations undertaken and recommendations for further investigation.
Geology of eastern Kenya
The details of East African geology are still being olarified, but the outline
of the geologic structure and history is now reasonably well-known. To help
understand the regional setting within which the Tana river basin is located, Plate 4
summarizes the general geologic situation. This map is based on information
obtained from several sources (references 1, 2, 3 and 4)» and was locally modified
to accord with observations made during the course of the present survey.
The basement system oocupies the central part of Kenya and forms the stable
platform on which the remainder of the country has been built. This system consists
primarily of metamorphic gneisses and meta-sedimentary rooks, with some intrusive
rooks. Most are of Pre-Cambrian age and have been severely folded and faulted at
various time during the long period since they were originally formed. Some of the
intrusive rocks, however, are known to be relatively young and were scarcely affected
by teotonio movements. On the whole, the basement system, in which are located all
of the damsites under consideration as far downstream as Koreh, affords generally
good foundation conditions and some materials suitable for construction of the works
envisaged.
To the west of the basement system, much of the oountry is composed of relatively
young (tertiary to quaternary) volcanic materials, which form the highlands of Kenya.
These voloanio rooks and ash break down to form fertile soils whioh are easily
eroded, particularly when stripped of their natural cover by cultivation or overgrazing,
with the result that muoh of the sediment carried by the Tana river is
derived from this upland area. Also within the volcanio zone are the rift valleys,
which are features of continental soale. They are related to geologic faults,
and most of the earthquakes of East Africa originate under or near these valleys
(5).
To the east, outorops of the basement system slope down under younger
(carboniferous or permian to tertiary) sedimentary rocks and even younger (tertiary
to reoent) sediments, as shown on Plate 4* The sedimentary rooks, whioh are locally
exposed in the southern part of Kenya, are mostly sandstones and limestones and are

-43-
very variable in their physioal properties. Younger, flat-lying sediments underlie
the site at Korokora and the surrounding area* From the engineer's point of view,
these sediments are predominantly soils, although locally they have been ohanged
to rook by the cementing action of calcium carbonate or by the irreversible
dessioation of hydrous minerals. Small bodies of intrusive rooks of various types
are present within the area of sedimentary deposits, although occurring less
frequently than in the adjacent Pre-Cambrian system.
More detailed information on the geology of eastern Kenya can be found in
several publications»notably in report No. 15 of the Geology Survey of Kenya (2).
The files of the geological offioe of the Water Development Department and of the
BP-Shell Petroleum Development Company of Kenya Limited contain the drilling records
from exploration for water and petroleum in eastern Kenya. Much of this information,
of course, refers to depths greater than those of interest for the purpose of this
report.
Published and unpublished information on the geology in the vioinity of the
various damsites will be referred to in connection with the description of each.
Seismology
Earthquake aotivity is common in the rift valleys of western Kenya, and, as
previously noted in Chapter III, areas bordering the Tana basin have, in the past,
reported earth tremors.
While only limited interpretation has been made of the available data, it seems
probable that earthquake shook will not be a serious consideration in the design
of dams and other major structures in the middle and lower reaches of the Tana river.
Prudent design, however, requires that the effect should not be neglected, and for
sites from Seven Forks to Koreh, some seismio forces must be allowed for, as well as
due consideration given to possibilities that earthquakes might induce seiches arid
landslides in reservoirs.
The ourrent information on seismology and the status of interpretation in and
around East Africa is reviewed in Section B 5.1 of Technical Volume JI (Appendix B),
and recommendations for appropriate design criteria presented.'
Eoonomio geolorar
The eoonomio geology of Kenya is reviewed in Section B 5»2 of Technical Volume II
(Appendix B). The most recent value of mineral production available is for the year
1959, in which mineral products accounted for some £ 5,352,000 (4), representing
just over two per cent of gross domestio production in that year. Investigations
are currently in progress to locate and identify new mineral deposits which may
contribute to the economio growth of the country.
As far as is known, there are no mineral deposits within the middle and lower
reaohes of the Tana which would be affected by the power and irrigation dams envisaged
in this report. Generally, good rock materials for construction purposes are found
close to all damsites from Koreh upstream. Some rather impure gypsum deposits, which
may nevertheless be useful for soil improvement, occur to the north of the irrigation
projeot area. It is oonsidered that there is likelihood of significant new discoveries
in the areas affected by the proposed power and irrigation oomplex of schemes.

-44- •
Elsewhere within the lower Tana, all known rock outorops of various qualities
liaVé leoii ejLaoiined for sources.or construction materials, for within the lower
catchment rock materials are generally scarce and remote from construction locations»
Geologio 3ite Investigations
To provide basic information in respeot of each potential power storage site
and at the main.diversion dam« geological exploration surveys were undertaken to provide
information on foundation conditions and looate sources of construction materials
in the vicinity of each development.
The main emphasis was devoted to determination of foundation conditions at
Korokora, the proposed site for diversion to the irrigated lands. The location of
a dam at this site, in a wide alluvial valley, poses special problems, and
determination of a feasible design required some knowledge of specific foundation
conditions and of the suitability of local materials for construction«
All other sites at whioh dams may be constructed lie upstream within the
exposed Basement rock oomplex of eastern Kenya, into which the middle Tana has
entrenched itself. Por the purposes of the present study, sufficient foundation
information for these sites was obtained by walkover surveys to correlate previously
published information, interpretations from aerial photographs and aerial
reconnaissance.
In Section B 5.3 of Technical Volume JÏ (Appendix B), the geology of the various
proposed damsites is described. Therein, it is pointed out that only a limited
amount of field work has so far been carried out at certain of the sites. The oost
estimates which have been made for this feasibility report must, therefore, be based
upon conservative evaluations of foundation suitability. Additional information
will be needed before details of design and refinement of cost estimates oan be undertaken.
Por Korokora and Seven Porks (Sections B 5«3«1 and B 5»3»7 of Teohnioal Volume II),
where considerable explorations have been made, recommendations for future work have
been included in the relevant descriptions. Por other sites, recommendations whioh
pertain equally to each are elaborated in Seotion B 5*3.9 of the same volume.
5.3 Cost Estimating Data
Estimates of oonstruotion costs for the various works described in later chapters
of this report must take into acoount local site conditions, availability of
construction materials, skilled and unskilled labour, and other factors peouliar to
the type of work«
Capital costs are separated in the estimates presented herein into direct and
indirect items. The former includes readily quantifiable work items supplied or
executed at site, such as excavation, rookfill, concrete and equipment. Indirect
items, on the other hand, are associated with the work to be oarried out but less
directly measurable. Such items as construction, administration and engineering,
and contingencies are inoluded in this latter oategory»

-45-
The appropriate unit cost data for estimating the direot cost items have been
derived from comparisons of recent large oivil engineering works in East and West
Africa, correlated with up-to-date Canadian cost data. It is of interest to note
that, by and large, on-site unit costs for heavy construction in various underdeveloped
countries are frequently quite similar to Canadian oosts, as determined
from recent comparative studies, and this is so for East Afrioa.
Indireot costs generally are estimated as appropriate percentages of the total
direot oosts from experience. Certain items ( notably roads)«however, are inoluded
with direct items, although estimated herein from unit oosts« Schedules of direot
and indirect cost estimating data are presented in Tables B 5-4 arid B 5-5 of
Technical Volume II (Appendix B). The unit rates quoted are in E.A. shillings
(1966 figures). r \y x . '
Annual costs are determined by the cost of money, the amortization period, and
the costs of maintenance, interim replacement and operation.
Throughout this report, the rate of interest has been taken as six percent, and
the amortization of permanent civil engineering works for both power and irrigation
developments as over fifty years. This, it is understood, accords with currently
acceptable practice for economic evaluations of power and irrigation developments by
the International Bank for Reconstruction and Development.
Certain works of more limited working or useful life have been amortized over
shorter periods, and in each instance, the amortization period is noted in the
discussion of the particular work concerned.
Maintenance and interim replacement and operation expenses are estimated from
experience data as percentages of capital cost, while neither inflation nor insurance
following construction are allowed for in the economic analysis presented in this
report. Further discussion of annual oost parameters is to be found in Seotion B
5«5«2 of Technioal Volume JX (Appendix B), and the periods and rates adopted for the
economic evaluation of development of power and irrigation are summarized hereunder.
Interest rate 6 perdent
Amortization
Power projects 50 years
Irrigation works 50 years
Buildings and tenant housing 25 years
R. and T. Centre pumping station
and temporary supply canal 4 years
Maintenance and interim replacement
Power projects 3/4 percent
Irrigation works, buildings,
housing, eto. 3-l/2 percent
Operation
Power station
Irrigation system
1/4 percent
1-1/2 peroent

-46-
SOILS AMD VEOETATIOff
CHAPTER VI
The lower Tana basin between Saka and Garsen comprises an area of approximately
3*000.000 acres, and it was necessary to select from this large area a smaller
project area for examination. Considerations of soils and topography in relation to
possible diversion sites resulted in the selection of an area of approximately
700.000 acres on the right bank of the Tana river, the southern boundary of which
was taken to be the L. Thowa-Galole. This forms the northern region of the project
area as discussed herein. However, subsequently it was found necessary to expand
the area surveyed to include an additional 300.000 acres of land south of the L. Thowa,
and this southern region is included in the project area as indicated on Plate 1.
Similar soil conditions obtain on both banks of the lower Tana and between the
east and west bank areas. The choice of the west bank was determined from considerations
of generally more uniform topography and the prospects for finding more
suitable soils under command of a diversion at Korokora for a lower dam and a shorter
main supply canal.
Within the broad limits of investigation, semi-detailed soil surveys were carried
out over the northern region, together with a vegetation survey. Correlation of
the soils-vegetation relationships and reconnaissance level investigations of the
southern region permitted the mapping of soil boundaries and interpretation of the
suitability of soils south of the L. Thowa Galole with reasonable confidence»
A detailed soil survey was made of the area selected for possible development
as a research and training centre to service the scheme throughout its development
period. Details of the soils and vegetation surveys are presented in Technical
Volume .Ell (Appendixes C and D respectively).
6.1 Semi-detailed Soil Surveys
The first phase of the soil survey consisted of more detailed reconnaissance of
the northern region. Analyses of soil samples and correlation with aerial photography
established the governing criteria and indicated that the semi-detailed survey should,
to a great extent, concentrate on those aspeots of geomorphologio development characteristics
of semi-arid conditions. Thus, the most significant soil profile factors
were found to be structure as related to salinity and alkalinity«

-47-
During the semi-detailed survey» soil samples were taken from test pits established
at approximately one-mile intervals along a grid of east-west trace lines spaced
approximately one mile apart* Soil chemistry analyses were performed on all of these
samples and the reports of these are presented in Technical Volume IV (Appendix E).
Boundaries of the soil units as presented on Plate C.2 of Technical Volume /IH
(Appendix C) were established from photo-interpretation on low-level photography
(scale approximately 1.10.000), flown after establishing the grid of trace lines and
identification monuments. It may be noted that in the soils maps there are some
inaccuracies as a result of the necessity to compile them from uncontrolled mosaics.
Nevertheless^ for the purposes intended} it is considered that the soils map and
.the derived land suitability map reasonably represent the situation with respeot to
soils throughout the project area«
The investigations revealed a completely irregular pattern of soil units which
have been classified in accordance with the Seventh Approximation System of the United
States Department of Agriculture (l). The classification adopted is presented in
Table 6-1, and it may be noted that the Great Groups and Subgroups distinguished in
the Seventh Approximation do not cover all of the soil units identified within the
project area. In order to complete the classification« a new Great Group, the
Halorthids, and a few new Subgroups« Typio Halorthids, ITatrio Grumusterts and Natrio
Grumaquaerts, have been introduced«
6.2 Detailed Soil Survey
A detailed soil survey was carried out over an area of approximately 13»000 acres«
shown in Plate 16 as the area intended to be the Research and Training Centre« The
lowest-lying parts, which are subject to periodic flooding« consist of heavy Young
Alluvial clay soils covered with grass and some trees at higher spots« The higherlying
soils of the Old Alluvial mainland consist of scattered, sparsely covered
ridges and flat« scrub-covered« plateau soils. In the depressions« heavy cracking«
clay soils covered with grasses and herbs are found. A transition between the
Orthids of the plateaux and the XJsterts of the depressions is found in local depressions
of heavy, non-cracking clay soils, identified as Vertic Natrargids.
The classification of the different soil units within the Research and Training
Centre has been determined with greater precision than with the semi-detailed survey
throughout the project area» due to the more accurate mapping, especially of the
vital nonsaline-nonalkaline top layer. Thus, further sub-classification of units
has been possible* as may be noted from the legend of Plate C.13 of Technical Volume IV
(Appendix C), and from Table 6-4«
6«3 Vegetation Survey
A survey of vegetation was carried out over the northern region of thé project
area to assist in the interpolation of soil unit boundaries. The identification of
soil-plant relationships should also provide useful information for the assessment of
ecological conditions throughout the area, affecting animal husbandry« forestry and
game migration*

0
L
A
L
L
TJ
V
I
A
L
T
0
U
N
a
A
L
L
U
Y
I
A
L
-48-
Table 6-1 - Soil Classification
Order Suborder Great group Subgroup
Mapping
symbol
Relative
topographical
position
Entisol Ustent Psammustent Typio Psammustent . PR Highest
Aridisol
o
Vertisol
Argid
Orthid
Natr argid
Typio Natrargid Hi'
N2
Mazio Hatrargid N3
Camborthid Typio Camborthid C
High
Halorthid Typio Halorthid S Transition
between high
and low
Ustert Grumustert Natrio Grumustert GÜ Low
Aquert Grum aquert Natrio Grumaquert GA Lowest
Eapludent
Typio Eapludent PL High
Entisol Udent Vertic Eapludent U
Regular ly
flooded soils
of the meandex »
plain-great
group of suborder
udent
US
P Lowest

-49-
The vegetative associates have been identified in relationship to the morphology
of the region and hence are readily comparable with the soil classification. The
major associations identified are given in Table 6-2.
The vegetation characteristic of the Old Alluvial part of the project area is
generally classified as grasslands and bushlands, the latter comprising species
adapted to the xerophytic environment. The riverine forest of the Tana flood-plain
is the only area on which are found trees of a size useful for construction or as
a significant source of fuel supply* The species present, however; are generally
slow-growing varieties and consideration must be given to the introduction of new
species to provide a local supply of fuel wood for any large-scale irrigation complex«
Tsetse flies have been identified in the Tana flood-plain and this trypanosomiasis
vector may penetrate into the semi-desert area along bush-covered beds or luggas.
Control of tsetse flies and other insect vectors may require clearing of the riverine
forest above and below the limits of irrigation development. In this way, reinfestation
of a major forest unit from outside the area may be avoided.
6.4 Land Classification
A land classification map has been derived from the soil maps, in which five
suitability classes of soils with respeot to irrigation have been distinguished. This
map (Plate C.3 of Technical Volume III A, Appendix C), identifies acreages of suitable
soils and their topographic relationship.
It may be noted that the acreage of suitable soils occurs in patches. This
feature is less pronounced toward the south and near the river, where large homogeneous
areas of irrigable land are found. To the north and west, the suitable soils of
Classes 1, 2 and 3 are intermingled with patches of Class 4 soils, which, for irrigation,
can be considered only marginally suitable.
Soils of Class 1 are considered to be very suitable for irrigated agriculture
and are not expected to present any special problems in the management of cultivation
practices. Soils of Class 2 and 3 suitability are represented by the soils on which
agronomic trials have been conducted at Galole; see Technical Volume ,V (Appendix F).
While these soils yield satisfactory crop returns, they generally present some
difficulties in management. Saline-alkali or alkali subsoils underlie the problemless
topsoil layer at shallow depth. It has been found to be essential to ridge these
soils to provide sufficient volume for root development. Careful management of
cultivation practices and control of irrigation water applications are essential
to prevent upward movement of the salts and formation of an impenetrable alkali
horizon.
Class 4 soils are considered to be only marginally suitable for irrigation
development. Such soils have been excluded from the irrigation even if reclamation
should prove technically feasible. Experience with these soils has been limited to
small scale observational trials at Galole, from whioh it is evident that only
shallow-rooting crops will grow in these soils, and even these require very special
cultivation practices. Thus, irrigation of these soils has been ruled out, except
insofar as very small patches have to be included in the layout to avoid fragmentation
of the irrigation units.

Mapping symbol of the
associations
-50-
Tahle 6-2 - Classification of the Vegetation
into Associations
Description of the association
1 Semi-desert scrub
2 Deciduous scrubland
3 Shrub thicket
4
Open bushland - dominated by Cordia
sp. near Gharaf and Acacia reficiens
4A Acacia bushland - usually Acacia
paolii or Acacia reficiens
4B Middle terrace grassland - dominated
by grass and herb species identical
to those of Association 4
4C Closed bushland - dominated by Acacia
reficiens. Commiphora spp., and
Euphorbia grandicornis
1/4
5
6 Shrub grassland
7
Mosaio of Associations 1 and 4 - often
dominated by Commiphora spp*
Thicket dominated by Terminalia
orbicularis
Valley grassland - dominated by
Sporobolus helvolus
8 Flood-plain - dominated by nongraminaceous
herbs
9
Flood-plain bushland
10 Tana riverine forest
11 Human settlement and cultivation

-51-
The acreage of soils over the 920,000 acres investigated throughout the project
area are presented in Table 6-3, together with a brief discussion of their characteristics
for irrigation. In Table 6-4» a similar presentation is made of the soil
suitability classification for the Research and Training Centre.
Apart from topography, the presence and depth of the leached nonsaline-nonalkali
topsoil primarily determines the suitability of the soil for irrigation. Causes and
consequences of saline and alkali conditions are discussed in Technical Volume III
(Appendix C). Leaching of the topsoil may lead to a solidified, impermeable, alkali
subsoil, especially where a high content of contracting olay occurs.
6.5 Reclamation
In order to reduce the salinity of soils, leaching should be considered. Calculations
have shown that great variations in initial leaching requirements exist, depending
on local soil conditions and the level of desalinization desirable. These requirements
may amount to as much as 2 feet 6 inches of water for one foot of soil. Given the
excellent quality of the Tana water for irrigation, the normal water requirements to
maintain and control the desired salinity level will be low and will probably not exceed
5 percent of the total field applications. It may be noted that, for saline-alkaline
soils, reclamation with gypsum has to occur simultaneously with leaching. Physicochemical
improvement of the alkali subsoil requires replacement of absorbed sodium by
calcium, for which gypsum is suitable. The amounts of gypsum required for de-alkalization
of the alkali soils over a depth of 2-1/2 feet vary, for the different soil types,
between 10 and 25 tons per acre.
The soluble sodium content in the irrigated water is low, and eight years of
continuous irrigation at the Galole Irrigation Scheme have shown a decrease in the salt
content of the top 3-1/2 feet of soil, and, moreover, a favourable, if only a very
small, replacement of sodium by calcium.
»*

Class
Suitability
for
irrigation
-52-
Table 6-3 (l) - Land Suitability Classification -
Project Area
Acreage
in
Project area
Soil classification
unit
1 Highly suitable 18,000 Typic Cambortbids C
2 Suitable 224,000 Typio Halorthids
Typio Hatrargids
3 Fairly suitable 323,000 ftatric Grumusterts
4
Marginally
suitable
and
Natric Grumaquerts
Vertio Hapludents
257,000 Typio Hatrargids
Mazio Batrargids
5 Nonirrigable 159,000 Typic Hapludents
Typic Psammustent8
Vertio Hapludents
Regularly flooded
soils of the
Meander Plain
Symbol
S
JU
GU
GA
u.
»2
H3
PL
PR
US
P

-53-
Table 6-3 (2) - Land Suitability Classification -
Project Area
Remarks
Deep. Porous. Nonsaline-nonalkali soils. Caliche usually
found at a depth of about 50 inches; this does not interfere
with permeability for roots or water. Light clearing and
levelling required.
Moderately permeable soils. Saline-alkali below fertile
topsoil averaging 16-inch thickness.
Sandy topsoil over 20 inches thick. Subsoil with impermeable
illuvial alkali hardpan, which does not interfere with root
growth and promotes water retention in topsoil layers.
Clearing of dense bush and levelling required.
Heavy contracting clay soils with porous nonsaline-nonalkali
topsoil of average depth 10 inches overlying slightly permeable
natric horizon impenetrable by roots* Topsoil is fertile:
puddles when wet. Levelling and careful ridging necessary:
light clearing.
Deeper nonsaline topsoil layer. Considerable levelling and
flood protection required.
Sandy topsoil less than 20 inches thick overlying impermeable
natrio horizon. Removal of hardpan cap and leaching to
reclaim not considered feasible.
Sandy topsoil and hardpan removed by erosion. Surface layer
frequently nonsaline-nonalkali as result of colluviation.
Areas with prohlemless topsoil layer more than 8 inches thick
more common in central and southern parts of project area.
Nonsaline-nonalkali levee soils of good quality: separated,
from old alluvial high terrace by low-lying river basin soils,
nonirrigable from gravity system proposed - subject to
flooding.
High-lying sandy ridges - infrequent dispersed locations.
Gullied streambed deposits: mostly planned in drainage ways.
Predominantly sandy river-wash deposits.

I,
Class Suitability
for
irrigation
-54-
Table 6-4 - Soil Suitability Classification -
Research and Training Centre
Acreage
in
R and T area
Soil classification
unit
Symbol
1 Highly suitable 1,615 Camborthid8 C
2A Yexy suitable 1,972 Typio Ealorthids
Vertio Hapludents
2B Suitable 1,510 Vertic Hatrargids N 4 - 1
3 Fairly suitable 4,653 Vertio Natrargids N*' 2
4A Marginally suitable 97 Typic Natrargids N 1 *
4B unsuitable 3,528 Typic Katrargids
Mazio Natrargids
The typic natrargids of the R and T centre have been inoluded in Class 4
suitability due to their limited acreage and unfavourable topograph!o
position. This is in contrast to the inclusion of typio natrargids in
Class 2 throughout the projeot area (Table 6-3).
S
U 1
N 2 ' 1
N 2 « 2
„3.1
H 3 * 2

AGRONOMIC STUDIES
CHAPTER VII
The Galole Irrigation Scheme was initiated by the Government in 1955 an( l expanded
to its present extent of 1,200 acres by 1964» Throughout its history, cotton has
been the sole cash crop of the scheme, although some tenants have grown irrigated
subsistence crops during the off-season.
The majority of tenants, drawn from the local riverine Pokomo people, have tried
to maintain their traditional flood-plain w shambas w l/ in addition to cultivating
their tenancies, generally to the, detriment of both« The consistent growth of cotton,
which up to I964 averaged about 1000 pounds per acre of seed-cotton, seemed to indicate
its general adaptability to the conditions»
Numerous other crops were suggested, agronomic experience and trials elsewhere
within East Africa and Kenya*s balance of trade in agricultural produots being taken
into consideration. The list of crops considered for trials in the applied researoh
programme of this survey included fibre crops such as cotton and kenaf; oil crops,
including groundnuts, soya beans, castor beans, sesame, safflower and othersj sugar
canej food crops such as maize, millet and sorghum; fodder crops, green manure crops,
and horticultural crops.
For purposes of economic evaluation prudence demands that the yield levels adopted
for the purposes of this report be conservative, particularly in view of the almost
complete absence of irrigation tradition within Kenya. Therefore, yields considerably
lower than those obtained under carefully controlled experimental conditions are
suggested, and, as may be noted in ChaptersyIX and X7I, an allowance has been made for
gradual improvement through experience and research by a net annual increase in
estimated yield of one percen-t.
To follow up the work started at Galole, recommendations were made to the Government
to continue agronomic trials beyond the period covered under this FAO/UNDP Survey.
In 1966, arrangements were concluded between the governments of Kenya and The Netherlands
l/ Shamba - Local term for small farm or garden.

-56-
to continue and expand the applied research initiated at Galole under this study
ust-il March 1969- In the zcantisc, thó Covéïïïïïèïvî, lia.» i-equeaieu a three-year extension
of this assistance. The objectives are to find out the extent to which the tenants
on the scheme are capable of adopting modern irrigation and agricultural practices;
to study effective management of the scheme; to train counterpart staff and to decide
on the measures necessary for the rehabilitation of the scheme. As the Galole scheme
is considered to be unrepresentative of the development area in that it contains
too high a proportion of good soils, the Government intends in due course to extend
the Galole scheme by another 1000 acres to include a larger proportion of poorer soils.
7.1 Cotton Experiments and Observations
Experiments were conducted into varietal choice, time of planting» spacing,
fertilizer requirements, weed control, insect and pest control, and the effect of
crop rotations. Each of these aspects is dealt with in more detail in Section F7.1 of
Technical Volume V (Appendix P).
The experiments to date have demonstrated that cotton grows well on the Typic
Ealorthidi/ and Natrio Grumusterti/ soils at Galole. Tields of well over 3,000 pounds
of seed-cotton per acre have been obtained within six months from sowing. The main
factors affecting yields are pests, weed control, and soil fertility. Fertilizer
trials indicate marked response to nitrogen; as shown by combined results, 200 pounds
of ammonium sulphate per acre increases the yield by 15 percent.
The production of cotton in the Galole scheme has been tied to cotton-growing
at the coast by a requirement to supply a medium long staple cotton to the ginnery
at Lamu. The excellent grade of cotton produced in the past has, to some extent,
predetermined the varietal choice.
Variety UK 51 was adopted throughout, apart from the varietal trials in the later
seasons. The vigour of this variety often results in excessive growth of stem and
leaf which tends to suppress boll formation. Further trials are required to find
a variety more suited to the climatic conditions of the lower Tana.
At the present time, interpretation of the yields and agronomic conditions suggests
that a tenant in a large scheme may be expected to produce 1,750 pounds of seed-cotton
per acre with variations from year to year between 1»500 and 2,000 pounds.
7.2 Experiments and Observations on Crops other than Cotton
As mentioned earlier, only cotton had been grown as a cash crop under irrigation
at Galole. Information on other crops that had been grown in the area was sketchy or
contradictory, so that research on other crops had to commence at an early stage of
the investigations.
1/ Typic Halorthid - Non-saline, non-alkali loamy topsoil of about 16 inches
overlying a saline-alkali subsoil.
2/ Hatric Grumustert = Heavy but porous, non-saline, non-alkali topsoil of
about 10 inches overlying an impermeable saline clay subsoil.

-57-
The list of crops that might reasonably be expected to offer prospects for successful
cultivation was large, and the time to test them limited. Therefore, in the first
season, a selection of the most promising crops was made for further study in formal
experiments during succeeding seasons, as described below. Details of the various
observation trials on these other crops are contained in Section 17.2 of Technical
Volume v„
Sugar cane
Sugar cane has been grown in Kenya for at least a hundred years, mainly along
the coast and near the shores of Lake Victoria, and small amounts elsewhere, where
the climate is favourable.
To obtain reliable data, at least five years of trials are needed, as well as
a large experimental area and a laboratory with a test mill. These conditions could
not be met at Galole. Moreover, except for some small plots growing canes of doubtful
origin, cane had not previously been grown in the area. Therefore, plant cane had
to be brought in from the Sugar Research Station near Lake Victoria, some 500 miles
away. Conditions for carrying out experiments were therefore far from ideal. Subsequent
trials under Dutch bilateral aid have not apparently been conclusive either
and there has been much damage by nematodes. It appears,therefore, that sugar to date
remains a doubtful proposition until more definite results are available. A tentative
estimate of yield based on trials so far is 35 tons of cane per acre containing some
4 tons of sugar.
Moreover, maintenance of planting and harvesting schedules would require the
provision of adequate labour and transportation facilities to ensure a steady supply
of cane to the sugar mills. Co-ordination of cane planting and harvesting would need
to be largely under the control of the mill organization to ensure continuous delivery
throughout the milling season. This need is also an argument in favour of using
plantation methods, rather than tenant cultivation.
Kenaf
Many attempts have been made in the past to grow soft fibres such as jute in Kenya.
None of tbese had proved successful, although kenaf (Hibiscus cannabinus) generally
seemed the most promising. Due to the lack of previous research, it was difficult
to obtain seeds of suitable varieties for testing in the early stages of the survey,
nevertheless, a small quantity of one suitable variety was obtained, with which
fertilizer trials were carried out. Several collections of varieties were later
tested on small plots.
The key to successful kenaf fibre production, once adequate yields of green stems
have been obtained, is in the reduction of labour requirements for processing of
the crop. Cutting and bundling of the stems, transporting them to the retting facilities,
stripping, washing and drying the fibre, if done entirely by hand, is excessively
demanding in labour. Economy in processing depends upon the introduction of meohanization,but
this will require close co-ordination with processing interests to ensure
production of an acceptable quality of fibre.

-58-
•Pii-rfhAT rfiBflapeh with ribboning and daeortieating maohinea ia required- a«
presently available equipment is not considered entirely satisfactory« Transport of
the green stems to centralized retting facilities would also require careful organization.
It is estimated that kenaf fibre yields of around 1,500 pounds per acre could be
obtained from tenants' fields after a growing period of about four months.
Groundnuts
Groundnuts are grown in practically every district of Kenya but only in a few
areas of the western and coast provinces does production reach a marketable surplus.
Research has been carried out mainly at the coast and in the Hyanza area, where numerous
varieties have been tested. Preliminary trials showed that growing this crop on low
ridges usually resulted in some waterlogging, and subsequent trials on higher, more
widely-spaced ridges, with two rows of plants per ridge, provedjnorei successful.
Seme varieties, especially in the earlier growth stages, showed a yellow leaf
discoloration over irregularly shaped areas of the field. The discoloration responded
to spraying with a one percent iron sulphate solution, although no improvement in
yield could be detected. It seems reasonable to assume that some varieties suffer
from iron chlorosis on these soils, whioh have a high pH value.
Ko statistically significant response could be shown to nitrogen, phosphate and
potash fertilizers, either singly or in combination. This lack of response is
compatible with the results of fertilizer trials with other crops. The absence of
response to nitrogen is in contrast to the noticeable influence of this element upon
yields with most other crops. This difference is explained by the abundant and active
rhizobium l/ of groundnuts.
High yields can be obtained with varieties whioh show a marked degree of tolerance
to local soil conditions. It appears reasonable to assume that yields of 1,600 pounds
of shelled nuts per acre could be obtained by tenant farmers. The growing season for
groundnuts is about 120 days.
Castor beans
Pour observation trials were carried out with a total of thirteen varieties on
two soil types. The highest yields (over 2,000 pounds per acre), were obtained from
two American dwarf varieties (see Volume V, Appendix P-ll). Insect attack occurred
as suspected with this crop and was kept under control by spraying with Thiodan.
But commercially this would be uneconomic. Also, a disease new to Kenya, which causes
defoliation, appeared, and so far no preventative has been found. However, further
research on this crop may well be justified in view of world demand for castor oil.
Groundnuts belong to the family of legumes, capable of fixing atmospherio
nitrogen by means of the baoteroid nodules in the root system.

Soy beans
59-
Trials with varieties of this crop were disappointing, a fertilizer trial showed
a marked response to nitrogen but no response to phosphate or potash» This result
suggested a lack of.bacterial nitrogen fixation, which would normally be expected with
this crop, as with' groundnuts. Indeed, at no time was any nodule formation found on
the soy bean roots, and several trials with seed treated with inoculants failed to
produce nodulation. This matter should be further investigated to find out whether
the inoculant was at fault, or whether the bacteria specific to soy bean cannot adapt
to the soils on which the trials were made»
Fodder grasses
Observation of six different fodder grass species showed that crops like Napier
grass and Signal grass had a high yield potential provided that considerable nitrogen
fertilizer was supplied regularly. For example, Napier grass could yield around 22
tons of field dry hay per aore per annum, but the total nitrogen application in the
form of sulphate of ammonia for this would have to be 900 pounds. However, without
nitrogen, 50 percent of this yield could be expected.
Maize
Twenty early-maturing varieties and hybrids of maize were tested initially in
an observation trial. Symptoms of nitrogen deficiency, as well as severe rust
infection, were observed. Stemborer attack was heavy but could be kept under control
with repeated DDT sprayings. The highest yield of 1,900 pounds of seed per acre was
obtained from variety Puccinia polysora resistant.
During the fourth season of trials maize was grown on the scheme under irrigation
and also on the riverine soils in small scattered plots. The maize crop on the scheme
failed convincingly due to stemborer damage, while the plots in between the riverine
vegetation were only slightly affected. The reason for this difference is not known
and would have to be determined by a thorough entomological investigation.
Sorghum
Twelve varieties of bird resistant sorghums, mostly developed in Uganda (Serere),
were tried initially in an observation trial. There was little borer damage, and
very high yields were obtained - up to 4»600 pounds of grain per acre. However, later
plantings in the rotation trials suffered from extensive damage by stemborer.
Rice
Rice is a popular crop along the Tana river flood-plain and many attempts are
made by tenants on the Oalole Irrigation Soherae to grow rioe on flooded land. Being
an important food and oash crop, it was thought advisable to inolude the orop in the
researoh programme. Unfortunately, it was only possible during the time available to
try out two local varieties under both wet and dry conditions. The results were

-60-
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are other varieties available in East Africa which should be tried, and a more thorough
search should be made for varieties from other parts of the world for continued trials
in the area*
Fodder, Green Manure and Cover Crops
The most promising species in this group of crops appeared to be cowpeas, velvet
beans, and sunhemp. These crops were easily established and grew rapidly into luxuriant
dense stands, giving large amounts of green matter for incorporation into the soil
and high yields of seed.
7.3 Irrigation Trials
Extensive irrigation experiments with cotton were performed to determine à suitable
irrigation regime for this crop, and, from observation trials, to infer water demands
for other crops.
Details of the irrigation trials may be found in Section F7.3 of Technical Volume .V.
From these trials, it has been found that a field water application of 2.5 inches with
an average 12-day interval between irrigations is most suited to the soils characteristic
of the trial ' fields at Galole, and has given satisfactory results with other crops.
In the particular case of cotton, this application is suitable for a ridge spacing of
40 inches with intervals of 16 inches between plants, growing at a density of two plants
per hole. Cotton yields were satisfactory and crop water usage was deemed to be more
efficient than for other regimens tested. These figures are exclusive of conveyance
and surface runoff losses, throughout the growing period. Applications must, of course,
he reduced, or the intervals between irrigations extended, to allow for effective
incident rainfall.
The heavy clay soils of the project area contract and crack extensively when dried
out. To grow crops on them in this condition, pre-irrigation is essential.
The foregoing requirements are used to determine the criteria for the capacities
of irrigation supply canals. Considerable work remains to be done, however, to refine
these preliminary proposals for irrigation regimes for crops other than ootton, and
to determine practical irrigation rules from field trials.
7.4 Animal Husbandry
The presence of large numbers of cattle, sheep, goats and camels within the lower
Tana catchment and adjacent plains of the Northern Frontier, suggested consideration
of possible improvements in animal husbandry production, either through provision of
irrigated pasture or by stall feeding with fodder crops grown under irrigation.

-61-
.It is estimated that, in the Tana river distriot alone, there may he about 70,000
cattle and 15,000 sheep and goats. The cattle are almost all of Zebu origin and
are considered to be some of the best indigenous stock in Kenya. This animal population
is constantly on the move, their nomad owners trekking annually many hundreds of
mile3 in search of water and pasture» Two major stock routes to the coast pass through
the lower Tana basin, the route east of the Tana river being preferred by reason of
better grazing and availability of water. Nevertheless, the western route, which
roughly parallels the Tana river in the vicinity of the proposed main supply canal,
is used extensively.
The long trek to the coastal markets generally results in severe loss of condition
and weight by all animals before arrival at the major buying centres - Lamu, Malindi
and Mombasa.
Tsetse fly is known to be present in the riverine forests of the lower Tana, and,
although not penetrating far outside this narrow belt, represents a hazard inasmuch as
lack of water often forces the herdsmen to drive the cattle to the river, even by day.
As indicated earlier, fodder crops, particularly grasses, grow well under irrigation.
It would be too hasty to assume that there is no future for animal husbandry
in the area considered for irrigation development»and the possibility of dairy production
should be considered. The scale of production feasible and desirable in relation
to the social and economic factors involved needs further detailed investigation.
Improved road communications into the interior of the lower Tana basin for irrigation
development will extend the market to the animal rearing area, and hence, in future,
these desert-reared animals may be sold in prime condition and trucked to the coast.
Development of the irrigation scheme may conflict with the traditional stock route along
the west side of the Tana river, and, while no great difficulties are foreseen, provision
of watering points for cattle along the main supply canal should be considered.

-62-
AGRO-ECONOMIC STUDIE S
CHAPTER VIII
Determination of a satisfactory crop rotation plan is dependent not only upon
the agronomic suitability of crops but also upon the costs of production related to
prices and prospective markets. Thus, from the agronomic and soil studies described
previously, an insight has been gained into the produce which might be grown and
the methods of crop production costs are reviewed.
For promising crops, an acceptable rotation plan may be proposed from an assessment
of costs and benefits. The system of land tenure proposed is also discussed
herein, as is the determination of appropriate tenant incomes and the means whereby
production can be achieved. Further details relating to all of the foregoing matters
are. presented in Appendix G of Technical Volume V.
8.1 Markets and Price Levels
Except for those products governed by international trade agreements, the world
market in recent years has not been particularly favourable for the disposal of
certain surplus agricultural produce. Free market prices have fluctuated markedly
over the years and current forecasts of international trade scarcely attempt to look
beyond 1970. Hence, although some part of the production from the lower Tana irrigation
scheme may have to be disposed of in this market, no valid forecast of prices
and demand can be made at the present time. For.the purposes of this report, there
is no alternative but to adopt the yardstiok of present prices. It may be noted,
however, that world prices for agricultural products have been relatively low in recent
years and it is believed that the use of current prices may result in a conservative
evaluation of scheme benefits, particularly as there is a growing recognition in
international trade markets of the interests of primary producing countries.
In recent years, consideration has been given to the formation of an East African
Common Market but, as yet, such a potential market has not come close to a reality.
There is little information available to indicate where production should be located
within such a market area, and for the present, therefore, its influence cannot be
taken into account.

-63-
The internal market of Kenya; however, can be more readily evaluated in terms of
population growth, and trends in income levels and consumption. Forecasts of population
growth are estimated in Table 8-1.
Tear
1965-
1970
198O
1990
2000
Table 8-1 - Population Growth Estimates - Kenya
Fertility unchanged
(hiRh)
Population Male labour
force
9,400,000
10,800,000
15,200,000
21,500,000
31,300,000
2,260,000
2,600,000
3,520,000
4,900,000
6,980,000
Fertility reduced
(low)
Population Male labour
force
9,400,000
10,700,000
13,200,000
15,800,000
19,300,000
2,260,000
2,600,000
3,520,000
4,490,000
5,280,000
Per oapita income is expected to rise by 3 percent per annum during the period
I966-197O, while the gross domestic product (ŒDP) is expected to rise 6 percent per
annum. These figures are based on the Development Plan (il), but the plan does not
offer any detailed comment on the long-term relationship between population growth
and per oapita incomes. However, in the absence of other information, assumptions
as to the long-term demand for certain agricultural products must be inferred from
the foregoing population forecast and past trends in consumption, for evaluation of
the eoonomics of development.
Cotton
Kenya cotton falls in the long to medium-staple range, and in the past has found
a ready outlet in the world market. Projections by the Cotton Lint and Seed Marketing
Board indicate that a favourable market will likely be available for such high quality
cotton for some time in the future. The domestic market at present consumes between
2 and 2.2 pounds of lint per capita annually, which is very low by world standards.
Presuming an inorease in consumption to between 4*5 an( * 9 pounds per capita annually,
as is found at present in many countries of the Near East and Latin America, projections
of the cotton requirements in Kenya in terms of the population forecast may be made
as shown in Table 8-2.

Year 4.5
Low rate.
-64-
Table 8-2 - Projected Cotton Requirements for Kenya in Tons
of Cotton Lint for High ana Low Projections of
Population Growth
lb
High rate
Per capita rates of consumption
6.5 lb
Low rate High rate
9 lb
Low rate High rate
1970 21,500 21,900 - — —
I98O 26,500 30,100 38,300 43,500 - -
I99O - - 45,800 61,200 63,500 84,800
2000 - - 56,000 88,800 77,500 123,000
Cotton has been included in the proposed rotation plan (see Chapter IX) and the
scheme might be expected to yield between 25,000 and 35,000 tons of lint annually
at full development. Such an amount of quality cotton may continue to find a ready
external market, with cheaper short-staple cotton being consumed locally. However,
it is apparent that the local market will provide sufficient demand to absorb most,
if not all, of the cotton production should the export market deteriorate, even if
substitution of synthetic fibres for a substantial part of the market is presumed.
The Cotton Lint and Seed Marketing Board controls production and marketing of
cotton and, at present, pays producers Sh 0.50 per pound for Grade AH seed cotton at
Galole grades as BR, due to the cultivation under irrigation and the hand picking
practised. Presuming a continuation of this method of harvesting, the ex-farm price
may be assessed at £ 61 per ton for seed cotton, when allowance is made for transportation
to Mombasa.
Sugar
Sugar consumption has been rising much more rapidly in Kenya than production, and
in recent years a substantial import of sugar has been necessary. At present, Uganda
provides about half of the sugar imported into Kenya, while the balance is purchased
on the open market abroad.
While the continuation of the recent 8 percent per annum increase in domestic
sugar production is not expected to continue indefinitely, projections indicate that
the total demand in Kenya by the year 2000 should rise to between 840,000 and 1,130,000
tons. The potential level of yield of the Tana scheme, if approximately half of the
area were devoted to the growing of sugar cane, has been estimated in the order of
650,000 to 750,000 tons but, as already indicated in Chapter 711, the possibilities of
growing sugar on the aoheme need further examination. If this quantity could be grown
it would find a profitable outlet in the local market provided the present protected
price is maintained. However, the creation of an East African Common Market may
influence the situation for Kenya sugar adversely, as it is understood that there are
substantial areas as yet undeveloped in Uganda which could produce sugar at a competitive
price.

-65-
The present internal price of £ 46 per ton at the faotory is tied to a formula
based on the Commonwealth Sugar Agreement price until the end of 1967* Thereafter,
it is expected that Kenya will re-price sugar to reflect local conditions rather than
continuing to adopt the CSÂ formula, which is based upon Caribbean costs of production.
Por evaluation of benefits from the possible growing of sugar cane in the irrigation
scheme, the present fixed internal price of £ 46 per ton at the faotory has been
adopted^ (See also Chapter,IX).
Oil props .
Of the oil oropa included in the experimental programme at Galole, groundnuts
performed sufficiently to be recommended for inclusion in the cropping pattern. In
addition, a useful edible and industrial oil can be extracted from cotton seed, which
is a valuable by-product from the cultivation of cotton.
At the_present__time, Kenya imports cotton seed and oil, but exports groundnuts
and oIi.~~Tt also imports palm oil and animal fats,* part of which could "be replaced"
by soft oil. The difference between imports and exports is, currently, a net annual
import of around 10,000 to 12,000 tons of soil equivalent. Recent per capita consumption
is calculated at about 2 to 3 pounds per annum, which is very low in relation to
world standards. At this level, income elasticity is high, so that prospects for a
growing home market are good.
For future producers in Kenya, there seems to exist not only a growing home market
but also a large potential world market. The present price for groundnuts averages
approximately £ 55 P er * on °f shelled nuts and this has been taken as the ex-farm price
for groundnuts produced in the project area.
Kenaf
Kenaf is a good substitute for jute in the manufacture of bags and cordage and,
as a commercial crop, has been quite successful in several countries. The current
prices offered to farmers for kenaf are £ 85 per ton for super grade and £ 75 per ton
for Grade A, f.o.r. at factory. Assuming road transportation from the project area
to the existing production facilities of the East African Bag and Cordage Company
at Thika, the price level in the project area is estimated to be about £ 65 per ton
for retted fibre, including the cuttings.
At present, it is not realistic to assume an export market for kenaf fibre, nor
to estimate when the local market might become satisfied. However, it is assumed
herein that the domestic market would be able to absorb the level of production
anticipated from the scheme if it should prove feasible to grow this crop on a large
soale^(See Chapter Ix).
8.2 Land Tenure
Before evaluating the size of farm holdings which may be suitable for planning
purposes, it is necessary.to make an assumption regarding the method or system of
land tenure to be adopted. Discussion of this matter was undertaken with representatives
of Government through the Tana Steering Committee.

- 66
As the investment neeaasATy to Aaya\nn +>» area ^iil d»»d hi£h stzuidcxds of
maintenance and consistently good husbandry with selected crops to achieve sufficient
benefits to «arrant development, settlement of independent farmers vas ruled out from
further consideration. Prospective farmers will require extensive training and
considerable guidance to achieve target levels of production* Therefore, a Tana River
Irrigation Scheme Authority, based on a Oezira-type institutional organization, operating
under the general policy of the Hational Irrigation Board, has been recommended by the
Tana Steering Committee* under this system, the tenant would have a leasehold on
property with succession rights, but not amounting to freehold* Such a system is
considered desirable to avoid fragmentation of holdings and to facilitate changes in
crop patterns and cultivation practices to meet changes in market demands*
To attract settlers to the scheme and retain them as contented farmers contributing
willingly,the rigorous and sustained effort demanded by irrigated cultivation
requires that income levels be sufficiently attractive* A cash income of £ 160 per
year, in addition to the social and institutional benefits to be derived from development,
is considered appropriate as the basic target income level for the average
tenant family.
8.3 Tenant Income and Labour Requirements
Government polioy with respect to the Tana irrigation project is to provide
accommodation for as many people as possible, and, at the same time, to size farm
holdings so that the average farmer can achieve the target level of income of £ 160
per year. This means that a labour-intensive type of operation must be considered.
A study was made of the labour input of a small group of tenant farmers during
the 1963 cotton season at the Oalole Irrigation Scheme to ascertain the average
capability of a tenant family. As a result of this study and similar studies by
others elsewhere in Kenya, it is assumed that the average tenant family of five will
be capable of providing 10 man-days per decade over long periods of time, and will
be able to provide between 15 and 20 man-days per decade during the planting and
harvesting seasons. In order to smooth out the total labour demand from the growing
of the various crops in the suggested rotation, it is necessary to consider the
input of additional manpower and some mechanization of operations. These matters are
considered in more detail in the following chapter*

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AGRICULTURAL DEVELOPMENT
CHAPTER IX
The classification of soils into their suitability for irrigation, as discussed
in Chapter yi ; indicates that only 2 percent of the project area contains soils of
Class 1 suitability, whereas Classes 2 and 3 soils together occupy some 61 percent
Despite the substantial total acreage of these soils, they are irregularly distributed
and, over much of the area, occur in a fragmentary arrangement with soils of Class 4
suitability. The latter are considered unsuitable for development because of the high
cost of reclamation, the additional water duty demanded, the extra husbandry requirements,
and their ultimately lesser crop yield potential. The incremental cost of
development and cultivation in combination with a lower level of return of Class 4 soils
would exceed the extra costs of extending the irrigation system farther south to
command sufficient acreage of soils of Classes 1, 2 and 3 suitability to balance the
ultimate water availability. Hence, agricultural development should be based on the
irrigation of soils of Classes 1, 2 and 3 only.
Areas of floodplain soils, which are physico-chemically equally suitable for
the growing of irrigated crops,as are the other soil classes, are subject to periodio
inundation,and the surface is generally more dissected by drainage channels. Thus,
most of the floodplain lands on the west bank of the river would be better suited to
the growing of fodder grasses under irrigation to support a local beef and dairy
enterprise to meet the local market. The remainder of the floodplain lands, it is
suggested, can be reserved for forestry activities,should suitable species be found,
thereby contributing to the local demand for fuel and minor construction materials*
9*1 Cropping Pattern
The cost of developing the area for irrigated agriculture, as described in succeeding
chapters, will be high, and thus together with the soils and agronomio factors,
points to the desirability of intensive use of irrigated lands to maximize the output
per acre* In the project studies the cropping pattern which was considered as a result
of preliminary trials at Galole was a 6-year rotation based upon cotton, sugar cane,
kenaf and groundnuts as major crops, as illustrated on Plate 6. In this an intensive

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-69-
use of land is planned, resulting in a cropping intensity of 2.0. Hhile this crop
pattern has formed the basis of the economic evaluation made in these studies, further
consideration of it has shown certain objections to some of its aspebts^and further
investigations are recommended . to evolve a pattern better suited to all the conditions.
These objections are discussed in the summary of conclusions and recommendations in
Chapter ^1.
9»2 Farm Size and Layout
The basic unit of agricultural development is regarded as a tenant-family holding.
Studies of manual labour and mechanical equipment inputs, and gross and net values of
production, in terms of the selected crop-rotation plan, lead to an assessment of farm
size and layout. As discussed in Chapter 7111, it is intended that the average tenant
should be able to obtain the target income of £ 160 from a smallholding, essentially
relying only on family labour. To achieve an intensive crop rotation, mechanization
of cultivation for field preparation and ridging, and additional labour would be
necessary. With these provisos, the tenant, together with his family, would find
productive year-round employment on a ^-acre holding, with an average labour requirement
not exceeding ten man-days per decade, but with up to twenty man-days per decade being
required during periods of harvesting and planting, at which times the entire family
are presumed to contribute to these activities.
Prom the layout point of view, 5-acre holdings fit conveniently into the irrigation
layout, in which 50-acre units form the basic module of development. Thus, two tenants
would share a 10-acre field served by one head-furrow (see Plate 7)« To further
improve the efficiency of management, each holding would consist of alternate 2.5-acre
plots, whereby half of each field would perhaps be cultivated under sugar cane for three
consecutive years, while the other half would be under cotton, kenaf and miscellaneous
orops during the same period. Every year, each plot in the soheme would be cropped
in accordance with one of the years of the rotation plan, with the phase reversed after
three years. Phasing of rotations and shifts in phasing along the irrigation sections
is proposed to even out peaks in requirements for irrigation water, labour and
machinery.
9.3 Requirements for Labour and Machinery
The requirements for labour and machinery have been estimated for the complete
6-year rotation cycle in 10-day periods. These studies indicate that the average
labour requirement will be less than 10 man-days per decade, with peak demands of up
to 20 man-days per decade during planting and harvesting. Machinery requirements are
based on the assumption that each tractor could serve 400 acres, allowing for a
maximum rate of operation of 8 effective hours of fieldwork per day, an average rate
of 1,350 hours per year.
In addition, for cane cutting, kenaf retting and soheme maintenance of oanals and
drains, a labour force of between 2,500 and 3,000 workers would be required for each
30,000-acre irrigation district. Such labour will not be readily available on a casual
basis in such a remote location, and therefore it is desirable that continuous employment
be offered to such labour gangs, as is provided for in the scheduling of the
rotation plan. Such year-round employment will avoid the social' problems and high costs
associated with the engagement of casuals for only short periods.

»LOCK 1
FARCCL ir S ACRM
»TAOr i or ooTATion
PARCEL or »ACBCJ
STAM t Or ROTATIOfl
riiLP
{°A'
LEGEND
Fia «IL unit» or »LOCK < TNC ROTATION »NASI
IS a-« «no TNC TIM« »MA»f li A,
II1PICATE0 »T R-I-A.(»IE AL»0 FLATC 4 )
TWO fABMtn» CULTIVATIH* TWt TMIBO M-ACBt PICL»
Or AN IRRIGATION UniT OP »0 ACRC3,
HOLOin« or A PARMCR CONSIST» or t nor».
GOVERNMENT OF KENYA
UNITED NATIONS SPECIAL FUWP
SURVEY OF IRRIGATION POTENTIAL
LOWER TANA RIVER BASIN
row «wo MRKULtyot oiMAmzATum or THC UJITCP BAIICH»
SCHEMATIC ARRANGEMENT OF ROTATIONS
AND
CROP PHASING RELATED TO FARM HOLDINGS

-71-
9.4 Value and Cost of Agricultural Production
The direct costs to the farmer for production of a specific crop are for seeds,
fertilizer and insecticides. For the various crops of the proposed rotation, direct
costs of production are estimated as shown in Table 9~1»
Item
Land preparation
Fertilizer
Seeds
Weed control (chem.)
Pest control (chem.)
Harvest-lifting
Bags
Decortication (shelling)
Table 9-1 - Direct Costs of Agricultural Production
Average crop cost - Sh per acre
Cotton Sugar cane Kenaf Groundnuts Beans
22
92
5
20
140
10
Miscellaneous
20 8 ' 8 5
Total
11
300 750 210 180 45
The indirect costs are those related to the general operation of his farm and
inolude purchase and maintenance of irrigation siphons and farm tools, a charge for
periodio applications of gypsum as a land reclamation measure, interest on credit,
and land and water charges. Weeding equipment, siphons, minor tools, plus an allowance ^
for periodic gypsum applications, are estimated to cost an average Sh 30 per acre per
year. The total demand for interim productive and consumptive credit is estimated
at Sh 600 per acre, which, averaged over the year, will cost the farmer Sh 30 per acre
annually, at an arbitrarily chosen interest rate of 5 percent. The cost of land and
water is the subject of discussion in Chapter XVII, wherein the eoonomio evaluation of
the entire scheme is considered in relation to its over-all viahility and the finanoial
situation of the individual farmer.
Although continuous oropping of the entire irrigated area is technically feasible,
it would be unrealistic to assume that this high level is always attainable. Hazards
from resistant strains of pests, plant diseases, slumps in market prioes and unfavourable
weather conditions will likely reduce the total effective crop aoreage and, on the
average, a reduction of 5 peroent in output has heen made as an allowance for suoh
oontingenoies in the eoonomio evaluation.
80
510 "
120
20
22
120
60
22
40
20
10
80
25
10
5

-72-
Based on the foregoing, average gross and net values of /production for the £-yeaï
rotation cycle can >>e evaluatsd as presented in Table 9-2, and indicate that the basic
initial net farm income will bejE 47*50 P©r acre.
These are based on the following expected rates of yield of major crops:
Crop Yield per acre
Seed cotton 1,750 lbs
Sugar cane 35 tons
Shelled groundnuts 1,600 lbs
Kenaf fibre 1»500 lbs
These rates are believed to be conservative. Cotton on the small Galole Irrigation
Scheme has yielded up to 3,000'ilbs/acre.
Table 9-2 - Estimation of Farm Income
Crop
Crop-7
acres
Per six-year rotation cycle
Gross
value
Direct
costs
Difference
in value
Shs '- ^ Shs Shs' Shs
Cotton 2.00 , 1,900 600 1,300
Sugar cane 3.00 3,990 750 3,240
Groundnuts 1.67 1,330 300 1,030
Kenaf (fibre) .67 350 150 200
Kenaf (seed) .33 200 70 130
Beans
Total
Average
Less indirect costs
Net value of farm production (gross
of land and water rights)
Less allowance for crop failures (about
5 percent)
Plus additional income from livestock
.33 70 15 55
8.00 7,840 1,885 5,955
1.33 1,307 314
993
60
Farm income (before payment of land and
water rights)
95O ,
933
43
890
60

9.5 Processing of Farm Products
-73-
The majority of the agricultural products obtained at farm level under the proposed
cropping pattern will require further processing. These activities include conversion
of sugar cane into sugar« seed-cotton into lint and seed« peanuts and cotton seed into
oil and cake* and kenaf fibre into bags. In order to maintain some flexibility in the
cropping pattern when economically or otherwise justified, it may be desirable for
the scheme authority to establish and operate some or all of the processing plants.
The concentration of production and the large quantities involved will provide an
opportunity to establish large-scale processing units.
To provide an indication of the magnitude of processing involved, an estimate of
the annual output from a 30,000-aore irrigation district has been shown in Table 9-3*
Product
Table 9-3 - Quantities of Produce to be Processed
(30«000-acre district)
Yield
per acre
Extraction
factor
Processed
product
per acre
Crop-acres
in
irrigation
district
Total
output of
processed
produce
- (tons) (tons)
sugar 35 tons
cane
4.00 15,000 60,000
cotton lint 1,750 lbs
seed
cotton
seed-cotton 1,750 lbs
seed
cotton
oils - cotton
seed
groundnuts 1,600 lbs
nuts
cenaf 1,500 lbs
retted
fibre
.35 .27 10,000 2,7O0!/
.60 .47 10,000 4,7O02/
(.47 ton) .15 .07 (10,000) 700^/
l/ Equivalent to approximately 15,000 bales.
2/ Either seed or oil.
.45 .32 8,000 2,600
.67 3,000 2,000

-74-
POWER POTENTIAL AND MARKETS
CBAPTER X
The development of a major hydro-electrio complex at Seven Forks near the upper
limit of the middle Tana represents the first significant development intended to
control and utilize the water resources of the main stem of the river. The proposed
complex of projects at Seven Forks will include a major storage reservoir to regulate
the natural flows of the river* It was recognized in planning the survey of the
irrigation potential of the lower Tana basin that the effectiveness of this and all
subsequent developments on the river would have to be carefully studied to determine
how each project would influence the downstream irrigation potential.
The long-term average flow of the Tana river immediately downstream from the
proposed Seven Porks complex represents only about one-half of the long-term average
flow estimated at the Koreh site, the lowest point on the river at which an economically
feasible hydro-electrio development could be constructed. Therefore, despite the
regulation implicit in the storage development planned at Seven" Forks, one-half of
the total flow of the river enters the main stem below this complex, and additional
storage must be developed farther downstream if the optimum irrigation potential of
the lower basin is to be realized. Thus, a study of the entire river has been carried
out to ascertain where further storage capacity could be developed economically.
Throughout these evaluations, due regard has been given to preserving the hydroelectrio
potential of the river. Insofar as it has been determined that the irrigation
potential of the lower basin may be realized by providing for uniform regulation
of upstream flows, with only limited storage capacity for re-regulation at the point
of diversion, there is no significant conflict of interest between irrigation and
power development.
10.1 Power Resources of Kenya
Before discussing the studies carried out to evaluate the benefits of developments
associated with power and irrigation on the Tana, it is the water power potential of
the Tana that should be placed in its proper relationship to the power resources of
Kenya.
In a recent review of the resources of East Africa (l), the hydro-electric power
potential of the country was estimated to total only 17*9 megawatts, apart from the
potential of the middle reaches of the Tana. This estimate comprises a number of small
developments varying in size from 0.2 to 4.5 megawatts.

-75-
The total power potential of the Tana river between Seven Forks and Koren is now
estimated to be some 800 to ipOO megawatts at 55 percent capaoity factor. Consideration
of the general hydro-meteorologic regime of Kenya and its rivers confirms that there
is little prospect for any substantial hydro-electrio developments elsewhere.
In the absence of any known fossil fuel resources, and with the geothermal potential
of the eastern rift valley not yet established, the Tana river represents the only
known significant power resource of the country. Looking into the future, after the
internal power resources of the country are fully developed, continuing growth of Kenya's
economy will ultimately depend upon importing energy, either in the form of fuel for
thermal or nuclear power stations, or through import of further hydro-eleotrio energy,
probably from Uganda, as more of the large potential recognized on the Uganda Uil e
is developed.
In terms of Kenya's economic development for the next two to three decades, it
will undoubtedly be necessary to consider development of the Tana power resources as
a means of conserving foreign exchange which.would otherwise be spent to import energy
in one form or another. Therefore, throughout the investigations of the irrigation
potential of the lower Tana, it has been incumbent upon the project to recognize the
necessity to optimize its hydro-eleotrio development insofar as is compatible with
other water demands.
Just as the Tana possesses the greatest power potential of any river in Kenya, so
too the prospects for irrigation in its lower reaches represent the largest potential
within the semi-arid regions of the Republic. With nearly three-quarters of the
country falling within the semi-arid zone, this important potential should also be
realized, if it oan be shown to be economically feasible, to support the planned growth
of the national economy.
The upper catchment potential for irrigation has already been investigated (2),
and appropriate reservations made by the Water Apportionment Board to secure for the
future the possibility of realizing the optimum development of these upper reaches. Bo
significant irrigation potential has been recognized in the middle reaches of the Tana
river and therefore the major foreseeable water uses below the Seven Porks development
will be in the realization of the hydro-electric potential of the middle reaches and
of the irrigation potential farther downstream in the lower basin.
The proposed Seven Forks hydro-electric project, as conceived in the 1959 report
of the consultants to the Power Securities Corporation (3), envisaged a complex of
three developments, as discussed in Chapter 3ŒI»
(i) The Re servoir development.
(iiJ The Gtaru development,
(iii) The Kindaruma development.
The Reservoir development was to consist of a rockfill dam, located approximately
3.5 miles above the confluence of the Thiba and Tana rivers. This project, developed
to a full supply level of 3»432;feet (Kenya datum), would have provided an estimated
total storage capacity of 935*000 acre-feet, of which some 820,000 acre-feet would be
live or usable storage. The development included provision of a powerhouse with a
planned installation of 40 megawatts«
The Gtaru development would consist of a low-level barrage across the Tana a
short distance below the Tana-Thiba confluence. Water would be diverted through a
headrace and pressure tunnel approximately 20,600 feet in length to an underground
powerhouse and thence returned to the Tana river through a 13,500 feet tailrace tunnel.
The total head developed in this way was to be 660 feet and provision was to be made
for an installed capacity of 170 megawatts in the powerhouse.

-76-
The Kinda-rnma développent ooûoisied or a low dam some 2.25 miles below the exit
of the Otaru tailrace tunnel, diverting water across a sharp l80 degree bend in the
river to a powerhouse located farther downstream. This run-of-river development was
planned to have an installed capacity of 30 megawatts and to develop a gross head of
approximately 120 feet.
In the consultants' revised report on the Seven Porks development (4)» the concept
proposed in 1959 remained substantially unaltered with the exception that the reservoir
dam would be built after the Kindaruma development, and be increased in height to
a full supply level of 3t438»5 feet, providing 935,000 acre-feet of live storage
capacity. In addition, some minor changes in planned turbine installation were indicated.
It was also indicated therein that the height of the storage dam could be
raised by a further 15»5 feet to provide an additional 450,000 acre-feet of usable
storage which, it was suggested, might be beneficial to downstream irrigation development.
The cost of this increase in dam height was estimated to be about £ 2,100,000.
In I964 FAO was requested to advise the Government as to the benefits to irrigation
of the live storage proposed for the Seven Porks Reservoir Development, and, further,
as to the desirability of requesting irrigation purposes. This advice was requested
as a matter of urgency in view of the imminent necessity to proceed with construction
of new generating capacity to meet the growing load demand of Kenya. Interim reports
(5, 6) dated July and September, 19^5» were issued to provide preliminary advice
on this matter.
It was also agreed that, in order to evaluate fully the benefits to irrigation
from storage at Seven Porks,it would be necessary and desirable for the PAO Tana
survey team to evaluate not'only the benefits from the proposed reservoir development,
but also the advantages, if any, of creating other storage at the proposed reservoir
site, or at an alternative site below the junction of the Thiba with the Tana, hereinafter
referred to as the Confluence Site. It was also agreed that the Kindaruma
development might proceed without prejudice to the upstream storage development, or
to subsequent development for power and irrigation downstream.
The East African Power and Lighting Company Limited, Power Securities Corporation
Limited and, subsequently, following its formation in July 1964, the Tana River Development
Company Limited provided the project team with additional reports, plans and
general information on the Seven Porks hydro-electric development (7, 8, 9» 10f H»
12, 13)* In addition, through their consultants, Messrs. Balfour, Beatty and Company
Limited, the power company provided basic topographic mapping covering the alternative
damsites under consideration and the river reach upstream to be inundated by the
various storage proposals. Additional technical details and comments have been received
through correspondence with representatives of the power companies and their consultants,
and in direct discussion.
As mentioned earlier, a significant hydro-electric power potential has been
identified in the middle reaches of the Tana river, downstream from the Seven Porks
complex. The total potential of the Tana river for hydro-electric development is
considered in Chapter XII and Appendix J of Volume VI. Therein, a complex of economically
attractive developments which could provide between 800 and 1000 megawatts of installed
hydro-electric capacity are discussed.
10.2 Present Kenya System
Electricity is supplied and distributed in Kenya by the East African Power and
Lighting Company Limited, and its associate company, the Kenya Power Company Limited.
Both companies operate under exclusive licence granted by the Government.

-77-
There are, at present« two separate main supply areas: Nairobi and western Kenya«
and the coast. The former comprises the larger system« with a total installed capacity
of approximately 102.7 megawatts, consisting of 25.94 megawatts of hydro-electrio
capacity« 36.37 megawatts of thermal capacity« and a net 40»4 megawatts of capacity
imported under bulk supply contract from the Uganda Electricity Board. It may be
noted that the hydro-electrio capacity is restricted in a normal minimum year to 15*5
megawatts« and in a year of absolute minimum flow to only 8.3 megawatts. The UEB
provide, at Tororo, 30 megawatts, under terms of a 50-year supply contract which
commenced in 1958, and a further I5 megawatts under a short-term supply contract. Of
the 36.37 megawatts of thermal capacity, a number of units are not now considered
reliable, and the remainder are to be maintained as standby reserve when new generating
capacity is constructed.
The coast system, oentred on Mombasa, consists of 46 megawatts of thermal capacity
in operation and currently under construction. The area served by this system extends
northward along the coast to Malindi and south to Likoni.
10.3 Load Growth Forecast
The load factor in 1962 for the Nairobi and western Kenya system was 65.8 percent
while for the coast system it was approximately 63.8 percent. Whilst interconnection
of these two systems has been considered, this possibility has for the purpose of this
report, been disregarded and the two systems have been considered as developing
independently. In 1963, the East African Power and Lighting Company Limited commissioned
Messrs. Merz and McLellan to carry out a comprehensive survey of the future market
for electricity in Kenya (ll). The forecasts of peak demand and energy requirements
indioate a general tendency for the "system load factor to decrease gradually to about
60 percent by 1980 and to remain relatively oonstant thereafter during the forecast
period.
It may be noted that the present high load factor for the Nairobi and western
Kenya system is achieved through off-peak heating of domestic water supplies utilizing
a ripple-current system. This has proved to be most effective in balancing the system
loads. However, future growth of the system is expected to result in a larger portion
of the demand arising from commerce- and light industry,^ resulting in a gradual over-all
reduction of the system load factor.
The power sequences studied in detail in Appendix J of Volume,71 have been scheduled
in accordance with an assumed rate of load growth similar to that forecast by Messrs.
Merz and McLellan, and as shown on Plate 8. However, the market for eleotricity in any
country is subject to fluctuations, depending on the state of the general economy.
This may, on the one hand, provide the stimulus for vigorous development, resulting
in a sharp increase in load growth or, alternatively, may have a restraining influence
on industrial growth, leading to a levelling off in the demand for power. It may be
stated, however, that even during periods of economio recession, past experience in
most countries of the world has shown that the demand for electricity has continued
to grow, though at a reduced rate.
Information on the growth of the Kenya system since I964 has shown that the rate
of increase in demand for electricity forecast by Messrs. Merz and McLellan has not
yet materialized. It is possible that this may be only a short-term trend, which
may change radically as a result of increased economic activity. Nevertheless, for
the purposes of the present report, it has been considered prudent to assess the effect

PEAK DEMANO (MW X K)0)
T
•
3
4
S
t
1
!
i
i
i
i
i
y
1
/
GROWT» RATE 1 / GROWTH IATE 2
GOVERNMENT OF KENYA
UNITED NATIONS SPEIIIAL FUND
SURVEY OF IRRIGATION POTENTIAL
LOWER TANA RIVICR BASIN
1 FOOD AHO ASMCUlTUIIt OMAMZATON OF TMC KHTD HAT10K»
« CO 1970 1980 1990 20 «0
NAIROBI AND WESTERN KENYA SYSTEM
ELECTRICAL DEMAND
PEAK LOAD FORECAST
ILA«> / ACRES
PLATE 8
i

-79-
of a somewhat lower rate of load growth on the economy of the power development programme»
Hence, on Plate 8, an alternate load growth curve has been presented, based
on an annual rate of increased demand of seven percent. Such a growth rate is
representative of more industrialized countries and is believed to represent the
lower limit of growth whioh may be expected under the development programme planned
for Kenya.
For the purpose of this report, a plant oapaoity factor, or system load faotor,
of 55 percent has been assumed in assessing the potential of hydro-electric projects
on the middle Tana.
10.4 Comparative Cost of Energy
In order to facilitate evaluation of potential hydro-eleotrio projects on the
Tana, a study has been made of the cost of providing energy at Nairobi from thermal
generating plants located at Mombasa. A separate analysis confirmed that transmitting
energy to Nairobi from plant located at Mombasa would be more eoonomio than installing
equivalent plant in Nairobi and shipping fuel from the coast. Units of modern
design, comparable in size to those anticipated for installation in the hydro-electric
stations, i.e. 30, 40, 50 and 60 megawatts, have been considered.
On Plate 9» the variation in at-plant oost of energy for units of various sizes
operating under different load factors is illustrated. For.comparative purposes, the
cost of thermal energy has been taken, in this report, to be represented by a 50
megawatt unit operating at a 55 percent load factor with an at-plant cost of production
of E.A. Sh O.O52I per kilowatt-hour.
To provide an estimate for transmitting this energy to Nairobi, the load forecast
prepared by Messrs. Merz and McLellan (ll) was used, and it was assumed that the Seven
Forks development would provide all requirements of the Nairobi area in the immediate
future. The existing generation, together with Seven Forks, would provide sufficient
firm capacity to meet the anticipated Nairobi and western Kenya load for at least the
next decade. It was assumed that thereafter a transmission system from Mombasa would
oome into operation and carry all the subsequent load growth.
Cost estimates were prepared for 275 kV, 345 kV and 400 kV schemes. In the case
of the 275 kV scheme, once the capacity of three lines had been reached, it was
assumed that subsequent construction would be at 500 kV. For the 345 kV and 400 kV
systems, later developments were assumed to be at 735 kV. The unit oosts of transmission
lines were based on the use of rigid steel structures since, although generally
cheaper, neither flexible nor guyed structure are suitable for use in an area infested
by large wild game.
The analysis indicated that the scheme operating initially at 275 kV provided
the greatest economy and resulted in a weighted average cost transmission of
E.A. Sh O.OI49 per kilowatt-hour transmitted from Mombasa to Nairobi.
The hydro-electrio power potential of the Tana may be developed independently of
any downstream irrigation complex, although, as noted in Chapter XII, the converse is
not true. While some indication of the probable rate of growth of demand for electrical
energy is available, the programme of irrigation development discussed herein
has yet to be approved. Hence, while alternative growth rates of irrigation have
been studied in terms of the earliest possible starting date to assess potential
conflict between the two major water users, power and irrigation, it may be noted
that there is, as yet, no firm commitment to initiate irrigation development by any
particular date. Therefore, the economics of power and irrigation developments have
been treated independently.

oc
UI
Q.
<
ui
o
CE
UI
as
ui
8
10
30 MEGAWATT
UNIT
40 MEGAWAJT
UNIT
50 MEGAWATT
UNIT
60 MEGAWATT
UNIT
-
i
S-21 E.A. «h. $
1
o'
ol
3
1
1
20 40 60 80 100
LOAD FACTOR PER CENT
GOVERNMENT OF KENYA
UNITED NATIONS SPECIAL FUND
SURVEY OF IRRIGATION POTENTIAL
LOWER TANA RIVER BASIN
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
COST OF ENERGY FROM
THERMAL INSTALLATION
AT MOMBASA

-81-
The power potential has heen evaluated in terms of the comparative cost of
energy produotion as delivered to the major load centre. Thus, for comparison with
the hydro-electric plants, the cost of energy delivered at Uairobi from thermal
generating stations has heen taken as E.A. Sh O.O67O per kilowatt-hour.
It may he noted that this cost does not take into account the effeot of the
somewhat lesser life of thermal generating plants, a much greater portion of the
capital investment and interim replacements in such ' being subject to the effects
of inflation. It has been suggested (14) that, under conditions of a long-term
inflationary trend of 2 to 2.5 percent per year, the actual cost of thermal energy
should be some 20 to 30 percent lower than that of hydro-electric energy at the
outset to be strictly comparable. Since such factors have not been taken into
consideration herein, it is considered that the comparison, when favouring hydroelectric
development, is valid and sufficiently conservative to outweigh any design
detail variations whioh may be introduced in the development programme.

-82-
WATER RESOURCES PLANHTKO ATO POTENTIAL
CHAPTER XI
It has already been shown that, on the basis of geographic and geologic
considerations, the Tana baBin can be subdivided into upper, middle and lower
catchments. This division is also convenient from the water resources planning
point of view since it defines an upper catchment within which some irrigation
potential and a few small power plants may be developed, a middle catchment in
which there is a very significant power potential but virtually no irrigation
potential, and a lower catchment wherein the development potential is essentially
agricultural.
In Chapters XII and XIII, proposals for development of the power resources of
the middle Tana and the irrigated agriculture potential of the lower Tana are
discussed in further detail. The planning aspects of utilizing the available
water resources to meet the needs of both of these major uses is discussed hereundor,
and in further detail in Technical Volume VI (Appendix i).
11.1 Water Resources for Power Development
The natural flow regime of the Tana river is reviewed in Chapters III and IV
and in more detail in Technical Volume II (Appendix A). Therein, a description
is given of the existing and future water demands anticipated within the upper
catchment. In Table 11-1 following, the long-term available gross flows and
the net available flows after deduction of reservations for anticipated use in the
upper catchment are given, together with design floods developed for the specific
projects to be discussed in succeeding chapters.
Prom the foregoing data, it may be noted that the average flow availability
on a long-term basis increases in a downstream direction up to the Koreh site, and
from that point onward the flows decrease. This factor is particularly important
in relation to the planning of water resources utilization. It is apparent that to
achieve maximum benefits through development of storage projects along the middle
Tana, these reservoirs must be located well upstream from Koreh.

-83-
Table 11-1 - Long-term Average FL oVB and Designs Discharges
Potential dam site Long-term
Average flow
Seven Forks - "Reservoir"
Seven Forks - confluence
Kindaruma
Kiamhere
Mutonga - upper
Mutonga - lover
Grand Falls
Adamson's Falls
Koreh
Korokora
cusecs
2310
3125
3125
3125
3660
4720
5130
5485
5580
4750
Net Net available available
potential flow l/
cusecs
1950
2600
2600
2600
3130
4190
4600
4955
5050
4220
Design discharges 2/
Potential Diversion
peak flood flood
rate rate
cusecs
115,000 33,000
150,000 42,500
150,000 42,500
150,000 44,000
170,000 48,000
200,000 57,000
250,000 138,000
320,000 138,000
350,000 138,000
250,000 110,000
l/ After deduotion of 36O cusecs from upper Tana flows and 170 cusecs
from Thika flows to allow for reserved allocations in upper catchments.
2/ Ignoring potential reductions by routing floods through storage upstream.
From Technical Volume VI, Appendix I, Table 11-1.
In the original studies made for the evaluation of combination of developments
which have been considered on the middle Tana, a simple waterbalance computer programme
was developed. This programme was used to simulate the flow regulation and
power outputs from various sequences of developments over the 25-year period of
synthesized and actual records from 1937 to I962, to facilitate the calculation of
benefits from particular levels of development at each of the sites considered.
To illustrate the foregoing, the average annual firm flows and energy outputs from
the Mutonga II system, sequence D, as discussed in Chapter XII, are presented in
Table 11-2.
11.2 ffater Resouroes for Irrigation Development
In Chapter XIII and in Technical Volume VI (Appendix K), the proposals for
development of an irrigation complex in the projeot area of the lower catchment
are discussed in detail. It may be noted that, whilst a complex of power developments
may be considered on the middle reaches of the Tana independently of downstream
irrigation, the converse is not true. From preliminary studies it was
evident that irrigation could not be economically Justified without the advantage
of regulation of river flows, which will be required in any case for the power
development, as a free benefit to irrigation. It has thus been eosential to
recognize the dependence of irrigation upon power, and to plan for maximum irrigation
complex consistent with the optimum power development of the middle river.

-84-
Tttule xi-d - Firm Flows and Energy Outputs - Tana River Developments
Mutonga II Sequence D
Development Full supply
level
Confluence
Kiambere
Mutonga
Grand Falls
Adamson's Falls
Koreh
Firm flow Annual energy
output
feet cuseos Gtfh
3,437
2,242
1,908
1,640
1,167
987
2,160
2,160
3,480
3,810
3,980
3,840
1,284
454
540
430
314
416
Total annual average energy 3,438
aBceecs
Successive construction of hydro-electrio power generating stations along the
middle Tana will result in a gradual increase in the available firm regulated flow
at the lowest power site on the river and, hence, also at the proposed diversion
barrage at Korokora. The use of this gradually increasing firm flow for irrigation
from Korokora is discussed hereunder to define the limits to the growth of irrigated
agriculture.
In determining criteria for the design of distributary systems for irrigation,
it is usually necessary to consider throughout peak rates of water demand. However,
the possibility of storing in the reservoir at Korokora river flows from the power
stations upstream when these exceed the current demands of irrigation, and thus make
them available to meet peak crop demands at other times of the year, makes it
feasible to plan the ultimate extent of irrigation development on the average rather
than the peak rates of requirement.
The basis for the evaluation of water demands discussed in this chapter is the
original crop rotation pattern as suggested in Chapter IX. Since this included a
considerable proportion of area to be under sugar cane, for which requirements are
heavy, the review and investigation of other cropping patterns now suggested cannot
result in increase of demand, as compared with the overall rates assessed for that
pattern. If anything, decrease seem rather more likely. For present purposes,
therefore, these overall rates may be used, and the peak rates used for the sizing
of canals. Vater requirements for individual crops were determined from irrigation
trials made at Galole. Combining these with pre-irrigation requirements gives
average monthly net water requirements (E.) as set out in Table 11-3«

-8 5
Table 11-3 - Monthly get Vater Requirements
Month Evaporation Crop
coefficient
-
Net vater requirements
(Bt in feet) feet (E. in acre-feet per aore)*
January 0.66 0.72 0.475 0.475
February 0.60 0.76 0.456 0.456
March 0.65 0.71 O.46I O.46I
April 0.60 0.62 0.372 0.338
May 0.62 0.62 O.385 0*385
June 0.56 0.61 0.342 O.342
July 0.55 0.56 O.3O8 O.308
August 0.59 0.54 O.319 O.319
September 0.61 0.74 O.45I O.45I
, October 0.63 0.83 O.523 O.523
November 0.61 O.84 •O.512 0.445
December 0.64 O.84 0.537 O.47O
* Deduction of effective rainfall allowed as discussed in Section A4.2.4.1 of
Volume II (Appendix A).
Taking into account the effect of orop staging and phasing over large areas
of irrigated cultivation, the average monthly irrigation requirements of the
project area have been determined for gross efficiencies of 50 and 60 percent.
The former efficiency is expected to apply during the initial stages of development.
Thereafter, a gradual improvement to 60 percent overall efficiency is anticipated
as tenants and management become more familiar with the operation of the system.
The numbers of acres which could be irrigated on this basis by each cusec
diverted from Korokora during each month of the year are presented in Table 11-4.
Table 11-4 - Monthly Irrigation Potential of Diverted Flow at Korokora
Irrigation Potential
Month Oross effioienoy Gross efficiency
50 percent 60 percent
acres per cusec acres per ousec
. of diverted flow of diverted flow
January 65 76
February 60 73
March 65 79
April 86 104
May 78 94
June 85 103
July 98 119
August 94 114
September 65 79
October 58 70
November 65 79
December 64
Average 72 -£-

Irrlgation potential
-86-
Although the progressive development of power projects in the middle Tana
will result in a gradual increase of the firm flow, the river will, in the future,
continue to suffer a net loss of water as it traverses the Hameye Swamp and its
meander plain between Koreh and Korokora. Although only limited information is
available, the few measurements which have been made, suggest that the present loss can
be accounted for entirely by évapotranspiration from the riverine forest,which is a
conspicuous feature of the desert landscape. Thus, in assessing the.irrigation
potential, an average net monthly loss of 50,000 acre-feet has been assumed to occur
between Koreh and Korokora. On the basis of this loss, which is equivalent to some
830 cusecs, the firm flows which would become available for diversion at Korokora,
as the power storage projects are constructed, are presented in Table 11-5«
Table 11-5 . ~ Flow Availability at Korokora
Firm Estimated firm Het firm flow
Stem of power out-flow flow entering to be available
development river downstream for diversion
at Korokora*
cusecs cusecs cusecs
Confluence 2160 1000 2150
Mutonga 3480 450 29OO
Grand Falls 3810 150 295O
Adamson's Falls 3980 Negligible 2950
Koreh 3840 — 2810
* Allows for approximately 83O cusecs loss between Koreh and Korokora, 100 cusecs
compensation flow at Korokora, and 100 cusecs average incremental evaporation loss
from the Korokora reservoir.
In terms of the two rates of power development which are discussed in Chapter
,X, it is possible to provide a schedule indicating the rate at which this increase
in firm divertible flow would become available.
Since irrigation growth will ultimately be dependent upon the availability of
regulated firm flows in the power system, it is also necessary to consider the rates
at which irrigation may be developed. For purposes of evaluation, two rates of
irrigation growth have been determined as illustrated on Plate 10* It may be noted
therein that Rate 1 easusec the steady development of 10,000 acres of newly reclaimed
land each year following an initial build-up over three years to the foregoing rate.
Bate 2 parallels Bate 1 for the first six years and then increases to 15,000 acres of
development per year for the next five years . Thereafter, further expansion would
take place at an annual rate of 20,000 acres.
In considering these potential irrigation rates, it has been necessary to keep
in mind that, for Kenya, development of a major irrigation complex such as is
proposod herein will be a pioneering effort. It will be necessary not only to construct
the physical facilities to undertake irrigated cultivation of crops, but also to train
adequate numbers of tenant cultivators and supervisory staff. Hence, while much
higher rates of irrigation development have been undertaken elsewhere, it is not
considered prudent to base the economic evaluation of irrigation development on a
faster rate óf growth than seems practicable under present circumstances.

o
QÇ
0>
400
350
300
230
•00
so
0
/ DEVEI .OPMENT
/ RATE N° 2
/
/ DEVELOPMENT
/ RATE N° 1
20 25 30 35 40 49
YEAR
GOVERNMENT OF KENYA
UNITED NATIONS SPECIAL FUNO
SURVEY OF IRRIGATION POTENTIAL
LOWER TANA RIVER BASIH
WOC AW ««»ICULTUHi OUtAWMTIOII OF THE UMTCO MTUB
RATES OF IRRIGATION
DEVELOPMENT
ILACO / ACRES
PLATE IO,

-88-
On Plate 11, the schedule at which firm flows would become available for
diversion at Korokora under the two rates of per«ox- growth discussed previously is
illuBi/rated, together with the growth in water demands to support irrigation in
terms of the foregoing irrigation development rates. Por illustrative purposes
only, it has been assumed on Plate 11 that crop production would commence in 1972,
which would require commencement of construction not later than 1970. Taking into
consideration the lead time necessary to determine the desirability of proceeding,
the arrangements for financing, the preparation of designs, and awarding of contracts
- for construction services and equipment, the foregoing date is considered to be the
earliest by which it is reasonable to assume a commencement of irrigation.
It may be noted that there would be little conflict between the water demands
if irrigation grows at the slower rate. An apparent conflict would arise if Growth
Bate 2 for power development occurred in combination with Development Rate 2 for
irrigation. However, the apparent shortage of water to the irrigation system under
such circumstances would, in fact, not arise, as the Korokora diversion dam must,
of necessity, contain considerable capacity for regulation in the early years of its
operating life. This capacity is eventually given up to sedimentation. In the
design of the diversion reservoir, as discussed hereunder, provision has been made
to store the sediment that would accumulate over 50 years.
Storage of the Korokora Diversion Site
Provision of regulating storage oapacity at upstream sites has been found to be
more economio than at the diversion site. Nevertheless, a limited storage capacity
must be provided behind the diversion dam so that re-regulation of water releases
from upstream power developments can be undertaken in conformity with the monthly crop
water demands noted in Table 11-^. : This re-regulating requirement amounts to some
-eight per cent of the total annual diversion volume, which, for a net irrigable area
of 300,000 acres, is estimated to be approximately 196,000 acre-feet.
As mentioned earlier, in addition to the foregoing re-regulating requirements,
sufficient capacity must also be provided to' accommodate deposited sedimentB which,
over 50 years, are expected to ocoupy some 600,000 acre-feet.
To provide the necessary re-regulating and sedimentation storage capacity at
Korokora, a crest elevation for the barrage of 470 feet has been selected in
combination with a minimum offtake elevation of 427 feet to the main supply canal.
The normal full operating supply level at Korokora would be at elevation 463 feet,
corresponding to a total storage capacity of approximately 750,000 acre-feet, which
is slightly less than the sum of the foregoing requirements. However, it is
considered to be adequate to support the irrigation development for the first 50 years
of its life, since during the initial development period less water is required,
and in the early years part of the sediment load could be passed through the Korokora
spillway by maintaining the operating level somewhat lever than the design full supply
level.
Ultimate irrigation potential
Based upon the available flow of the Tana river, excluding present reservations
for upstream use, the ultimate limit of irrigation development is estimated to be
some 250,000 acres. However, as has been noted in Chapter IV recent planning by the
Ministry of Agriculture suggests that much of the upstream 'reservation may in fact
become available to downstream power and irrigation development.

4000
CA
ü_ 3000
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o
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tooo
1300
300
ESTIMATED AVERAGE DEMAND FOR 300,000 ACRES .- 3430 :.F.«
ESTIMJ TED AVERi ME 0EMAN0 FOR r \
X
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-90-
As discussed in Chapter X. fn? purposes of «valuation it has been assumed herein
tuai, as much as 400 cusecs of the 530 ouseos of the 530 ouseos of recent reservations
would, in fact, become available. Should this prove to be true, irrigation might be
extended to approximately 280,000 acres. In addition, as discussed in Chapter XII,
diversion of the Athi river would contribute a significant benefit to the power
complex, and the regulation and the use of the diverted flow, up to a limit of a net
575 cusecs, is considered to be feasible. Under these circumstances, taking into
consideration both the foregoing additions to the present flow availability in the
Tana, an ultimate potential irrigation development of some 330,000 acres may be
contemplated.
Therefore, in the eoonomio evaluation of the ultimate potential irrigation
development as discussed in Chapter XVI of this report, two levels of irrigation
development have been considered, 250,000 and 300,000 acres. These two levels serve
to demonstrate the degree of economic feasibility of large-scale development and
also illustrate the significance of the rate at which development ocours upon the
economic viability.
In other projects, elsewhere, it may be found that irrigation development is
planned on less than absolute assurance of water supply. Consideration of this
aspect has been given to the development proposed herein. Whilst it has been found
that, at intermediate levels of development of the power oomplex, a reduction in the
requirement of reliability of irrigation flows would permit some expansion of the
irrigation complex, the flow utilization achieved would have become so high that a
further extension of the irrigation system, based upon reduotion of reliability to
even 80 percent, would net not more than one percent additional irrigated land*
Hence, in the economio evaluation, no further account has been taken of the slight
extension of irrigation facilities possible through allowanoe for a reduction in the
reliability of water supply.
11.3 Implications of Vater Resources Development
Inevitably, full exploitation of the water resources potential will change the
natural regime of the Tana river significantly, and these changes will reflect upon
the way of life of the population, who are dependent upon the river for their
livelihood. Except in the lower river, the effects of development are considered
to be entirely benefioial. It is evident, however, that along the lower Tana floodplain,
the indigenous Pokomo would find their traditional way of life untenable, as more and
more of the available water is diverted. These changes would not only reduce the
semi-annual floods on which much of their cultivation depends but also virtually
eliminate the use of the river for local transportation and fishing.
Nevertheless, as discussed in Section III.3 of Technical Volume 71 (Appendix I),
the value of water to power and irrigation is considered to be so significant es to
warrant solving the sooiologi? problems which might arise in moving and rehabilitating
the present riverine population.
It is impossible at the present time to do more than speculate as to the possible
effects of changes in the flow regime and upon the hydraulic characteristics of the
lower river. Between Koreh and Korokora, for purposes of present evaluation, an
average long-term loss through évapotranspiration of some 830 cusecs has been allowed.
It is evident that there is a considerable potential benefit being lost to irrigation
development through this circumstanoe.

-91-
It may be noted that, under the changed flow regime which would be imposed upon
this reaoh of the river through upstream regulation, the frequent overbank flooding
would be gradually eliminated in most years and therefore lesser'losses from the higher
areas of the Hameye swamp may be anticipated. Conversely, a higher average yearround
flow stage may result in an inorease in peroolation into the lower-lying areas
of the floodplain because the river gradient is superelevated throughout much of
its length. It is not possible at the present time and state of knowledge to predict
the net result of these opposing effects, and it has been assumed herein that the
net ohange would be negligible.
However, it will be important to assess the effect of long-term variations in
hydrologio regime as they occur, in order that, at such time as the irrigation
development is approaching full utilization of the available water, it will be
possible to consider whether some conservation of flows may be aohieved by appropriate
remedial works. Should this be possible, some further increase to the ultimate extent
of irrigation development may well be feasible.
Within the lower river below Korokora it is evident that, as the irrigation
oomplez grows, the river itself will be gradually reduced to a minor stream except
at times of extreme flood. Under such ciroumstances, it may be expeoted that the
riverbed will aggrade, that vegetation will encroach upon the present channel, and that
in consequence the conveyance capacity of the river channel will decrease. Thus, it
may be expected that, over the long term, the occasional catastrophic flood, which
would not be retained within the reservoir system, would cause even higher flood stages
in the lower valley than at present. Therefore, in planning for any future use of
flood-plain lands for forestry activities, irrigation of pasture lands or other
purposes, this potential hazard must be borne in mind.

-92-
POWER DEVELOPMENT
CHAPTER XII
As has been indicated elsewhere in this report, the water resources potential
of the Tana river for power and irrigation development represents a substantial
part of the total of such potential in Kenya. Evaluation of the interrelationship
between development of the middle and lower catchments of the Tana for both of these
purposes is essential if optimum pover and irrigation developments are to be defined.
It is important to recognize that, while power generation in the middle reaches
of the river may be considered as an independent development, it is not possible to
consider a large-scale irrigation complex as such. To be even marginally favourable
in economic terms, the irrigation complex must ultimately be as large as may be
practicable, and its size is fundamentally dependent upon the amount of storage
provided upstream. As is shown in this chapter, this regulatory storage is, in
any case, essential to the optimum development of the power complex itself.
Since it is possible to consider development of the Tana river to meet the
anticipated future demand for power, whether or not irrigation development is to
be realized, evaluation of the economics of the hydro-electric power complex has
been dealt with separately. Since it has been well beyond the scope of the terms of
distribution systems, the selling price of energy has not been determined. Hence,
the economics of power development have been evaluated in terms of the comparative
cost of energy produced and delivered at the load centre at Nairobi to meet the
growing demand for the Nairobi and western Kenya power system. This approach is
considered to be valid, recognizing that the irrigation scheme could not possibly
be economic if any of the costs, based upon total user benefits of providing storage
facilities for power, were chargeable to irrigation.
The selection and evaluation of sites leading to an economically viable programme
of development of six major power projects, in addition to the Kindaruma project
currently under construction, is described in detail in Technical Volume VI (Appendix j)#
Capital cost estimates for each development are presented, together with analyses
of the various sequences of development, leading to selection of the one which .
could best meet the future power load growth. The modified flow regime from this
sequence has been adopted for evaluation of the downstream irrigation potential.

-93-
12,1 Selection of Storage and Power Sites
. f- •
In Chapter XI, it is shown that the regulation of river flows is essential
if a substantial portion of the power and irrigation potential of the river is to he
developed* Since regulating storage capacity is essential to "both resource uses,
it is readily apparent that it will he desirable to achieve as high a rate of flow
utilization as possible upstream from the major power reaches so that the regulated
flow available to all downstream developments will be as large as economically
practicable.
Examination of topography and geology, in conjunction with flow analyses,
indicates that the potential for developing large-oapacity storage reservoirs and
major power projects is confined to the main stem of the middle Tana from Kamburu
to Koreh Hills. The upper catchment and tributary streams to the middle Tana offer
only limited opportunities for construction of storage projects, because of the
steepness of the terrain and the variability of the flows* In terms of the magnitude
of storage required for optimum resource utilization, such minor projects can be
eliminated from further consideration.
Immediately below Kamburu, the river descends some 650 feet over a river
distance of about 15 miles*. This drop occurs around a loop in the river course
within the Seven Forks area, where, for many years, attention has been focussed
upon a variety of schemes for developing the power potential.
At the lower end of the middle Tana, the Koreh Hills form the most downstream
location having a significant topographic control feature at which a power dam can
be contemplated. Below Koreh, the river suffers a progressive loss of gross
available flow through évapotranspiration losses from its floodplain as it traverses
mile after mile of semi-arid desert lands.
On Plate 2, the profile of the main stem of the river is shown, and reaches
between Kamburu and Koreh, which are considered to have significant power and
storage potential, have been identified thereon. In Table 12-1, the head and
long-term average flow in the middle reaches of the Tana are summarized, and indicate
that, in terms of gross power potential, the Kamburu to Mutonga reach is by far
the most significant.

-94-
Tabje, JL2"J. ~ Head, Flow and Power Po-fcggtial cf ths Mi dól o xana
Long-term
Hiver River average Gross Gros s
Site mileage eleva­ flow at head in power ^_
tion station reach potential*'
Tana Power -
Station 418 3,450
ft . cusecs ft HP
to 250 59,000
Kamburu 392 3,200 2,600
to 1,560 595,000
Kuntoga
to
Grand Falls
to
Eoreh
335
321
240
1,640
1,49P
810
4,200
4,600
5,050
150
680
63,000
321,000
QHe
* Computed as HP - 8.8 n rhere H is the gross head in the reach, and Q the
long-term average flou r at the downstream end of the reach. Efficiency
e is takeni as 80 per c ent.
1
; ,-
Total ;
2,640 1,029,000
It would, of course, be impracticable to use completely the long-term average
flow through the gross head as indicated in Table 12-1. Nevertheless, with some
50 percent of the maximum long-term average flow concentrated in the river at
Kamburu and over 80 percent at Mutonga, the relatively large portion of the total
power potential that is concentrated upstream from Hutonga focusses attention upon
the desirability of achieving the maximum economic utilization in respect of both
flow and head within this reach.
Preliminary studies indicated that the cost of energy at Nairobi from potential
storage power developments on the middle Tana would likely exceed that from alternative
thermal sources. However, it was also apparent that the regulation available from
such storage would result in economically favourable costs for power generated at
a number of downstream run-cf-river projects and hence, in terms of the system cost ,of
energy, bring the development of hydro-electric potential on the Tana into a oost
range competitive with thermal power«
i

-95-
In all some ten projects on the Tana have been evaluated. Not all of these
are independent, since some are alternatives to others in the same reach. The
projeots considered, grouped by reaches, as shown on Plate 12, are:
Upper reach of middle Tana — Reservoir
Otaru
Confluence
Kindaruma
Central reach of middle Tana - Kiambere
Mutonga (run-of-river)
Mutonga (storage)
Grand Falle
Lower reach of middle Tana - Adamson's Falls
Koreh
In addition, sinoe power generation and irrigation will ultimately be limited
by water availability, diversion of surplus flow of the Athi river into the Tana
catchment has been considered.
In Technical Volume VI, (Appendix J), the considerations relative to site
evaluation and the determination, of the costs and benefits from various combinations
of developments and their interrelationship are discussed. In Table 12-2, estimates
of capital costs for various levels of development of all the projects considered on
the Tana river are summarized.
The foregoing sites have been considered in various combinations of sequences
and levels of development and lead to selection of the Mutonga II sequences, as
illustrated in Table 12-3» as the most appropriate. Of the several Mutonga II
systems as discussed in Seotion J12.4 of Technical Volume VI (Appendix j), sequence D
is considered to be the most appropriate for optimum utilization of the power resouroes
of the river. In Tables 12-4 and 12-5, the power whioh may be achieved from this
particular sequence, under circumstances whereby additional flows are made available
through release of present upstream reservations and diversion of the Athi river,
are presented. Also shown in these tables are the comparative cost of energy at each
site and the total system, as development proceeds under the two rates of load growth
discussed in Chapter X.
On Plates 13 and 14 the installation schedule for the basio Mutonga II sequence
D power system is illustrated for each of the two rates of load growth discussed
earlier, and on Plate 15 the accumulated capital expenditures for this basio sequenoe
under the two growth rates is illustrated. Therein, it may be noted that the foregoing
basio sequence would meet the fast rate of load growth until well after the middle
1980*8} and, taking into consideration the additional flow and energy generating
capability through release of upstream allocations and diversion of Athi flows, into
the 1990's. The basic power system of the Mutonga II sequence D under the slower
>• growth of energy demand, _Bate 2, as shown on Plate 14, would be sufficient to meet
the internal requirements~"of the Nairobi and western Kenya system until well after
the turn of the century.

H -o\
\ ~ ~
PLATE 12

-97-
Table 12-2 - Estimates of Capital Cost - Tana River Power Pro.iect
Development Full supplylevel
Reservoir
Reservoir
Qtaru (low
Reservoir)
Qtaru (high
Reservoir)
Confluence
Confluence
Confluence ,
Confluence .
Formal maximum
tailwater level
Total oost
ft ft £
3438.5
3454
3260
3260
3392
3412
3437
3455*
3260
326Ó
2558
2558
2558
2558
2558
2558
13,178^000
15,098,000
18,149,000
18,849,000
30,317,000
34,617,000
41,828,000
51,138,000
Kindaruma 2558 2450 7,240,000
Kiambere
Kiambere
Kiambere
Kiambere
Eiambere
Kiambere
Mutonga
Mutonga
Mutonga
Grand Falls
Grand Falls
Grand Falls
Grand Falls
2192
2192
2192
2242
2242
2242
1867
19O8
1964
1640
I665
I69O
1725
1867
19O8
1964
1867
1908
1964
I64O
I640
I640
1455
1455
1455
1455
14,704,000
14,542,000
14,380,000
17,786,000
17,622,000
17,459,000
14,932,000
20,523,000
28,795,000
15,593,000
18,802,000
22,425,000
28,656,000
Adamson's Falls 1163 1040 14,256,000
Koreh.
Coreh
987
1007
810
810
16,866,000
18,953,000
Athi River Diversion 4415 4382 2,120,000
* Estimate provisional d lie to limitations of site data

ICOUCNCC * tCOUCKCC •
UMMN - l.'M
H.MI,M
*M
M
JM
».M
i.tt
• VTMU • .M'
lt.Mt.MI
•M
M
m
t. M
•.IT
• • '
« w nus • '.••
it.m.M
m
•i
«il
i.rt
l.l»
IMOM'I ' IUI I.IU
IO.Mt.Mt
m
•i
w*
* »
t.»
"—i
«M» - HT
• 1« K» . i.ot».
• ».MO. 000 i »9 .MO. 000
m
M
•n
t
• i
«Il '
M
«1
1.« i LU
I.H
I.U
•
•ont •. eut m MU» «nu it nmis» n t.*. MIU>M UNI H» •.*•••
t. tH MHMItrt IMtULU (»«'!» Ml HMtKT «*t ff IHM«. IT !«•
uni. 'Kun ut MUfCTi IM«I n« um •••um.
TABLE 12-3
MUTONGA II - SEQUENCES OF DEVELOPMENT
IIMHH • t.w
it.IM.MB .
Mt
•1
»l
«.Il
• M
r^r u
tt.m.Mt
Ht
Ht.
Ml
t.l»
I.«
'
MM» (IUI • I.Mt
•I.M.Mt
KMUftS *l lltl - «.V.l.
• iMtlUt» CIMCIT* il un . «.*.
• tatuim (Ulam umin • a.t. • «il t
• CMT f (KM! tï lltl • Mit I
• MMfM Cttl m WW • Mil •
sequence o
•IMKM • I.M
H.MMM
«M
M
M*'
t. M
t.U
.Ht
tt.m.Mt
Mt
ut
«• t. it
*.u
M. i '
MM» MU» • I.Mt
II.Mt.Mt
«M
M
Ml
I.M
t.n
IMMM'I P1U1 • LUI
o.nt.Mt
i»
M
•M
•.«1
UNI - Ml • MBU • I.MT*
irtn.Mo a.iM.tM
«ii •M
M
m
i.tt
I.M
rn
I.lt
I.M

LOAD GROWTH RATE
COWFLUEWCE - 3.127
CAPITAL COST
ENERGY - GWH
CAPACITY - I«
TOTAL CAPACITY - Ml
SITE COST OF ENERGY
TOTAL COST OF ENERGY
KIAMBERE - 2,242
CAPITAL COST
ENERGY - QMH
CAPACITY - MM
TOTAL CAPACITY - MM
SITE COST OF ENER6Y
TOTAL COST OF ENERGY
MUTONGA - 1,908
CAPITAL COST
ENERGY - GWH
CAPACITY - MM
TOTAL CAPACITY - MM
SITE COST OF ENER6Y
TOTAL COST OF ENERGY
»AND FALLS I ,610
CAPITAL COST
ENERGY - GWH
CAPACITY - MM
TOTAL CAPACITY - MM
SITE COST OF ENERGY
TOTAL COST OF ENERGY
ADAMSONS' FALLS - 1.163
CAPITAL COST
ENERGY - OWN
CAPACITY - MM
TOTAL CAPACITY - MM
SITE COST OF ENERGY
TOTAL COST OF ENER6Y
KOREN - 987
CAPITAL COST
ENERGY - GWH
CAPACITY - MM
TOTAL «PACITT - MM
SITE OF ENERGY
TOTAL COST OF ENERGY
TABLE 12-14
SYSTEM POWER OUTPUT AND COST WITH VARIATIONS IN
LOAD GROWTH AND NET WATER AVAILABILITY
MUTONGA 11-0 SEQUENCE
FAST SLOW
MUTONGA 11-0 SEQUENCE • «00 cfs
ADDITIONAL FLOW
FAST SLOW
£5«,785,000 £63,594,000 £58,101.000 £69,073,000
1,28« 1.284 1,520 1,520
270 270 270 270
270 270 270 270
6.60 7.115 5.87 6.80
6.60 7.45 5.87 6.80
£18,800,000 £19,400,000 £24.600.000 £25,600,000
454 454 538 538
94 94 225 225
364 364 495 495
6.30 6.50 6.96 7.23
6.52 7.14 6.15 6.95
£22,123.000 £22,750.000 £22,123,000 £22,750,000
540 540 602 602
112 112 112 112
»76 4?6 607 607
6.16 6.34 5.53 5.70
6.43 6.96 6.01 6.63
£16.369,000 £16,716,000 £16,389.000 £16.716,000
430 430 475 475
89 89 89 89
565 565 696 696
5.80 5.93 5.25 5.35
6.33 6.78 5.90 6.46
£14.769.000 £14,940,000 £14.769.000 £14,940,000
314 314 346 346
..'•'•• 65 ' 65 65 65
630 630 761 761
7.11 7.15 6.45 6.51
6.42 6.83 5.96 6.45
£17.875,000 £17,879,000 £17.515.000 £17,879.000
416 416 470* 470
87 87 87 87
717 717 848 848
6.20 6.31 5.62 5.72
6.40 6.78 5.91 6.37

LOAD »ROWrH
CONFLUENCE DEVELOPMENT FSL
CAPITAL COST - ATHI DIV.
CAPITAL COST
ENERGY - 6WM
CAPAC fTY - MW •
TOTAL CAPACITY - MW
SITE COST OF ENERGY
TOTAL COST OF ENERGY
KIAMBERE - 2.2»2
CAPITAL COST
ENERGY -GWH
CAPACITY - MW
TOTAL CAPACITY - MW
SITE COST OF ENERGY
TOTAL COST OF ENERGY
MUTONGA - 1.908
CAPITAL COST
ENERGY - GWH
CAPACITY - MW
TOTAL CAPACITY - MW
SITE COST OF ENER6Y
TOTAL COST OF ENERGY
GRAND FALLS .6» O
CAPITAL COST
ENERGY - GWH
CAPACITY - MW
TOTAL CAPACITY - MW
SITE COST OF ENERGY
TOTAL COST Of ENERGY
AOAMSONS' FALLS - .113
CAPITAL COST
ENERGY - GWH
CAPACITY - MW
TOTAL CAPACITY - MW
SITE COST OF ENERGY
TOTAL COST OF ENERGY
KOBEN - 987
CAPITAL COST
ENERGY - GWH
CAPACITY - MW
TOTAL CAPACITY - MW
SITE COST OF ENERGY
TOTAL COST OF ENERGY
'FM MUTONGA 11-0 SEQUENCE.
TABLE 12-5
SYSTEM POWER OUTPUT AND COST WITH
ATHI RIVER DIVERSION
ÄUDITIONAC FIRM FLOW - ATHI RIVER DIVERSION
200 cfs 575 cfs
FAST* SLOW* FAST* SLOW*
3,»37 ... 3, »55"
£ 2.2»0.0OO £ 2,330,000 £ 2.2HO.OOO £ 2,330,000
£56,»»3,000 £6«, 96», 000 £63.909.000 £76,8|9,000
1,390 . 1,390 1.630 . 1,630
270 270 320 • 320
270 270 320 320
6.S0 7.»3 6.25 7.20
6.S0 7.»3 6.25 .7.20
£20,600,000. £21,300,000 £23,700.000 £2»,600,000'
»97 »97 575 575
l»l 191 192 192
»II »II 512 . 512
6.30 6.52 6.27 6.51
(.«$ 7.19 6.25 7.01
£22.123,000 £22.750,000 £22,123.000 £22.750,000
570 " 570 630 630
112 112 112 112
S23 523 62» 624
S.«» 6.01 5.28 • 5.14
6.30 6.90 6.05 6.66
£16.389,000 £16.716,000 £16.389.000 £16,716.000
»52 »52 »9» »52
M 89 89 ' 8 9
612 612 713 713
*•** 5.6» 5.05 5.15
6.16 6.71 5.90 6'.»5
£l».769.000 £l«.9*0,000 £l».769.000 £|H,940.000
330 130 359 359
65 « 65 ' 65
677 •77 778 ' 778
6.77 6.81 6.21 6.27
6.S 6.72 5.92 6. »3
£17.179,000 £17.679.000 £17.575.000 £17.879.000
»M »36 »79 »79
87 87 87 .87
76» 7»» 865 865
6.0t 6.1» 5.52 5.62
6.22 6.65 5.87 6.31

-1 or-
; This very significant power potential whiob, if fully developed, may yield
up to 1,000 megawatts of capacity at 44 percent load factor, is undoubtedly one of
the major natural resouroes of Kenya, and, regardless of whether or not the irrigation
development, as discussed hereinafter is considered sufficiently attractive to
warrant development, has been shown to be self-justifying.
: Therefore, in all future planning it is recommended that the power potential
represented by this river should be preserved for the benefit of the country. It
must be recognized' that it has not been possible, within the terms of reference and
the time available, to evaluate in detail the optimum role and plant installation of
each project within the basic, sequences described. Nevertheless the Kutonga.II
sequence D is fundamentally suited to the optimum development of the power potential
of the river. Further studies of the integration of this power complex with downstream
irrigation should permit evaluation in detail of the future role of each plant
within the Kenya power system. Such a sequence study would be facilitated through
development of a more sophisticated mathematical computer model than that used fori
these preliminary studies. Such a model will permit optimization analyses of all
facilities, including transmission and distribution. Potential interconnections with
the ooast or other power systems should also be evaluated.
It will be appropriate, when such a system study is initiated, to review in ;
detail the projected load growth forecasts, and provide for updating and periodic
review as the system develops.

o
X
» 9
.a
o
z
<
4
Ul
0.
1*60
NAIROBI AND WESTERN KENYA SYSTEM
KOREH B7MW
2000
GOVERNMENT OF KEN VA
UNITED NATION» SPECIAL FUND
SURVEY OF IRRIGATION POTENTIAL
LOWER TANA RIVER ÎASIN
FOOD »«0 »MICULTUSE OKAmZtTlOII OF TNi! URITEO NATIONS
DEVELOPMENT SEQUENCE
MUTONGA ITD
INSTALLATION SCHEDULE
LOAD GRQWTH RATE I

o
o
I
too s
GOVERNMENT OF KENT»
UNITED NATIONS SPECIAL FUNO
SURVEY OF IRRIGATION POTENTIAL
LOWER TANA RIVER BASIN
FOOO MO »MICULTU« OKMIUTIO* OF TNI UHItlO UTIOIS
DEVELOPMENT SEQUENCE
MUTONGA HD
INSTALLATION SCHEDULE
LOAD GROWTH RATE 2
PLATE \A

I-
— 1 1 — i i —
1
•
: i
!
l
r~ r—i

-105-
IRRIGATION DEVELOPMENT
. CHAPTER XIII
In Chapter XI the ultimate irrigation potential of the lover Tana "basin is
estimated to he at least 250,000 acres. An increase to over 300,000 acres is considered
possible if reduction of the present upper catchment allocations and diversion of the
Athi river flows are acceptable to the Government of Kenya. Therefore, these two
levels of development - have been selected as the basis on which to assess the
economic evaluation of large-scale irrigation from the lower Tana.
Apart from the recent floodplain deposits, the lower basin,a large portion of the
project area,consists of fragmentary patches of suitable soils intermingled with
unsuitable soils. Thus, of a total of 349,000 aores of soils considered suitable for
irrigation within the northern region of the project area, only some 136,000 acres
occur in : contiguous relationships which permit reasonable economy in the layout of an
irrigation network. Hence, development of at least 164,000 acres of suitable soils
is presumed to be practicable south of the lower Thowa.
From reconnaissance soils surveys, it is evident that essentially similar
conditions prevail with respect to soils and topography throughout the southern region
of the project area as are to be found in the northern region between the lower Thowa
and the lower Hiraman. There is little doubt that similar soil types persist beyond
the southern limit of the surveyed areas, so that it is reasonable to presume that
water and not soils will form the ultimate limitation to irrigation development*
The proposed layout of the irrigation and drainage.network, and the internal
road system and townsites for the region north of the lower Thowa are illustrated on
Sheets 1 and 2 of Plate 16, while, on Sheet 3, the general alignment of major conveyance
canals for the southern region is indicated.
The Korokora diversion dam, the irrigation and drainage networks and suitable
fann-to-market roads, as well as land clearing and levelling, are considered as
essential features of the ultimate potential of irrigation development. Detailed
consideration of these aspects has been possible only for the northern region of the
project area, for which considerable information on soils, drainage and topography
has been gathered. Nevertheless, sufficient reconnaissance information has been obtained
for the southern region to permit reasonably reliable extrapolation of cost estimates
to cover development to a level of 300,000 acres.

-106-
13«1 Potential Devaioptent - Lajoal of irrigation Network
As indicated on Plate 16, the irrigation network envisaged comprises three
types of conveyance canals» The primary main-supply canal would lead water southwards
from the Korokora reservoir to the west of the Tana river, and the secondary
section-feeder canals would command the lands between this main canal and the Tana
floodplain. Tertiary block-feeder oanals, drawing from night-storage reservoirs,
would convey water to the irrigable lands in accordance with daily irrigation
demands at the field level.
The main-supply canal would offtake from the head regulator at Korokora at a
full supply altitude in the canal of 427 feet above sea level and would follow a
gentle gradient for some 38 miles southward until it reached the northern limit of
the project area at which point it would lie some 11 miles west of the Tana floodplain«
Thereafter, it would continue southwards, feeding the seotion canals which .
would offtake at intervals of about 3.5 miles« Seotion canals would flow eastwards
and feed into a herringbone pattern of block-feeder canals through night-storage
reservoirs located at approximately half-mile intervals. The block canals would
convey water to the unit-feeder canals which, in turn, would supply the field headfurrows.
Irrigation on the fields would be accomplished by siphoning water from
these head-furrows into the individual field furrows.
As indicated on Plate 17» a mirror-image pattern of drains would interlock
with the distribution system to return surplus irrigation water and runoff from
the fields to the main channel of the Tana river. The drainage system has been
designed to handle surplus irrigation water together with one-day maximum storm
rainfall at a recurrence interval of once in three years« A portion of this return
flow can be applied to the irrigation of portions of the flood-tolerant forests and
fodder crops.
The general configuration of irrigation canals and drains is illustrated schematically
on Plate 17. Therein, it may be noted that an irrigation unit of 50 acres
is proposed as the standard unit of development. This unit is divided into five
10-aore fields. Each field comprises two 5-acr« parcels which, in turn, are subdivided
into two plots of 2.5 acres« A tenant's farm holding of five acres consists
of alternate plots«
Determination of the daily duration of irrigation activity is fundamental to
the design of the irrigation network. Field application of irrigation water during
hours of daylight only is believed to be fully justified from considerations of the
intensive cropping pattern proposed, the lack of irrigation tradition among Kenyan
cultivators, and the relatively high cost of water as delivered to the field. These
factors favour the adoption of a daily application schedule, although it is recognised
that the cost of development is thereby somewhat increased through the need to
provide night-storage capacity within the irrigation system.
Experience with daylight operation in the Gezira and other Nile irrigation
schemes has shown that less wastage of water and higher crop yields result from such
a system. The improved control of irrigation practices by day leads to an increase
in benefits, which more than offset the additional .cost of night-storage reservoirs.

(ril ^ -^

-110-
Thô large developments of irrigation in the Sudan are probably the most
representative of the operational and water management problems to be ezpeoted in
the proposed Tana development* The generally high standards of operating efficiency
maintained in the Gezira development are in distinct contrast to recent experience
with new projects such as the Khashm el Girba project on the Atbara river and other
schemes in the Sudan which have been designed for continuous irrigation throughout
twenty-four hours of each day. It must be recognised that the considerable experience
in irrigation practices developed over the last fifty years in the Sudan has
nonetheless not in all cases resulted in efficient adaptation of the ouiti va tors to
such practiceso Floodings of fields or complete failure to irrigate occur (through
insufficient control of night-time operations) and result in reduotion of orop
yields.
As a matter of Government policy, the Tana Steering Committee has confirmed
a deoision to make provision in the design for daylight irrigation» Hence the
layout} as presented herein, has been designed for irrigation during daylight hours
only, which, for the equatorial location of the scheme, are considered to be essentially
a uniform twelve hours daily throughout the year.
Alternative locations for night-storage within the system were considered in
the studies. It was concluded that night-storage reservoirs located adjacent to
the section-feeder canals at the head of each blook-feeder canal is the most economio
arrangement. The alternative, to provide suoh oapacity within the blook-feeder
canals themselves, as is the praotice in the Gezira scheme, was found to be more
costly, although offering certain operating advantages. It is believed that the
night-storage reservoir system can be readily adapted to the cultivation practices
and the rotation plan, or to variants of it as presented herein. The proposed
arrangement requires refilling of the blook canals before irrigation can begin again
each morning. Since control weirs are necessary along the block canals immediately
downstream from eaoh irrigation offtake, it has proved practicable to design these
controls to retain some water in the canals overnight. This allows for rapid filling
and start-up of the system each morning as required by the irrigation schedule.
Prom the foregoing, it follows that the main-supply canal and all section-feeder
canals can be designed for continuous flows throughout the twenty-four hours of each
day. Block-feeder and field-distribution canals must be designed for twelve-hour
operation, with the night storage reservoirs providing hydraulio balance to the whole
system. The design of the irrigation network is discussed in detail in Technical
Vol.VI, Appendix K, wherein eaoh canal type and its controls are described, and
appropriate cost estimates for development are presented. It may be noted that, in
the design of the entire irrigation conveyance system, all canals have been sized
on the basis of the initial irrigation efficiencies discussed in Technical Volume VI
Section K13.1.1.3 of Appendix K, with the exception of the main-supply canal which,
in itself, must be designed for the ultimate conveyance capacity anticipated.
The net irrigable areas commanded by eaoh of the section feeders illustrated on
Plate 16 are summarized in Table 13-1«

Section feeder
canal
-Hi-
Table 13-1 - ffet Irrigable .Areas Commanded by Section Feeders
Old Alluvial land Floodplain land Total
acres acres acres
I 7,300 1,200 8,500
II 9,000 2,000 11,000
III 13,400 3,200 16,600
IV 10,000 2,700 12,700
V 10,200 - 10,200
VI 17,500 - 17,500
VII 42,700 - 42,700
VIII
(forth of L. Thowa
16,800 - 16,800
126,900 9,100 136,000
Is 9,900 - 9,900
lis 47,100 6,000 53,100
Ills 39,900 - 39,900
IVs (part)
South of L. Thova
11,100 - 11,100
108,000 6,000 114,000
Total 234,900 15,100 250,000
Completion of IVs
plus Vs
50,000
50,000
Ultimate total 284,900 15,100 300,000

-112-
13.2 Potential Dev^Topssst - Gx-imndwater Conditions and Drainage
The drainage requirements for irrigation schemes in general are determined
from considerations of both surface and subsurface flows. Throughout the project
arsa, the very limited information available suggests that, with the exception of the
perched water table found in the Tana floodplain, there is no groundwater near the
surface. Seep exploratory holes drilled at widely dispersed locations have encountered
mostly saline water at depths of.between I50 and 200 feet. It is also common to find
small quantities of groundwater in the sandy stream beds of luggas long after each
rainy season. The latter provide a major source of water during dry periods for
the cattle herds of the nomadic tribes.
Experience in irrigation schemes elsewhere has shown that water-logging may
develop over a long period of time. However, there are two reasons which suggest that
changes in the present groundwater situation in the project area would occur only
•very gradually. First, sloping-furrow irrigation promotes losses by surface runoff
rather than through deep percolation, even in cases of gross inefficiency in water
application. Secondly, the rather impervious nature of most of the soils will tend
to inhibit deep percolation. Consequently, construction of a drainage system for
control of groundwater has not been considered to be necessary in the present evaluation«
It is, however, advisable to provide for the removal of rainfall, runoff and excess
irrigation.
It is recommended, further, that studies of subsoil stratigraphy and groundwater
conditions should be undertaken and the changes in levels and qualities of groundwater
should be observed from the initiation of development so that, if necessary, steps
could be taken to prevent any tendency to waterlogging developing.
13*3 Land Preparation
Clearing and land levelling of the fields to be irrigated will be necessary.
In estimating the costs of these activities it has been asBumed that clearing of an
area some 25 percent greater than the net area of irrigated lands will be necessary.
Grubbing of only^the net irrigated area has been considered. The available information
on topography is not sufficiently detailed to determine with any reliability the
extent of land levelling which may be required throughout the projeot area to facilitate
irrigation with long field-furrows. Nevertheless, the detailed surveys carried
out for the Research and Training Centice have indicated that the general layout as
presented herein is reasonably representative of what may be anticipated, and is
believed to be satisfactory. In the irrigation layout it has been assumed that as
average furrow length of 500 feet will be appropriate. However, shorter or longer
furrows may have to be adopted in certain areas.

-113-
Levelling must he carefully planned in view of the shallow depth of nonsalinenonalkaline
topsoil prevalent throughout much of the project area. Therefore, land
planning to smooth out minor surface irregularities may be all that is practicable,
and the adoption of shorter field furrows would necessitate the provision of an
additional head-furrow in each field. For the purposes of this report, it has been
assumed that half of the net irrigable area will require some form of land levelling
and this will average some 200 cubic yards of earth movement per acre. It has been
recognized that the levelling of floodplain lands will, in fact, be more oostly than
for the remainder of the lands throughout the project area. However, the minor
additional cost for the small area of floodplain lands included in.the proposed
development has not been estimated separately,since a detailed land survey was not
available. In any case, a less elaborate distribution system for irrigation of
floodplain lands is all that will be necessary, as only flood-tolerant fodder crops
to support local dairy enterprises are contemplated for cultivation on the floodplain
soils. The unit cost estimate of development of floodplain lands has been made equal
to that of the remainder of the project lands.
13.4 Road Network
The internal road network throughout the project area north of the lower Thowa
is illustrated on Sheets 1 and 2 of Plate 16. In addition to those shown, the
network includes block and unit roads to complete the farm-to—market system. External
communications are proposed through development of a major truck road linking the project
area to Mombasa, and relocation óf the Nairobi-Garissa road to pass through the
Eandelongwe Hills and connect the project area directly to Nairobi.
The internal road system, consisting of section, block, and unit roads is
shown on Plate 17. It is recognised that the successful operation of.the scheme will
require adequate farm-to-market communications. In the original studies made for the
project, it was assumed that traffic densities would justify paying with stone section
roads for the two main north-south roads through the scheme. It is possible that the
time may oome when this is found to be so, but in view of the local conditions and of
experience in similar conditions elsewhere, earthen roads throughout the scheme should
be adequate to begin with. They could be graded and cambered, with suitable provision
for drainage. With appropriate maintenance, it is to be reasonably expeoted that they
could be open for traffic almost all the time, exoept possibly for short periods
immediately after considerable rainfalls. If a suitable method of soil stabilising
can be applied, so much the better. The estimates of cost presented in the second
column of Table 13-2 assume the construction of earth roads.
In the economic evaluation of irrigation development, all internal roads have
been considered to form an essential part of the projeot oosts, whilst the external
road connections to Mombasa and Nairobi are oonsidered to be part of the general
development of the national road system. However, it has been recognized that the
Mombasa-project area link will be needed for the oonstruotion purposes before it is
required for the normal transport of goods and persons. Henoe, a charge to irrigation
development has been included whioh is equivalent to the full operating and
maintenance charges for this road up to the time at which some 100,000 acres of
irrigated land would be in production. It is believed that thereafter the oonstruotion
of this road would be justified by the volume of traffic generated between the
soheme area and its entrepot, Mombasa«

-114-
The full cost of derslcpssüt or a quarry road between the Eandelongwe Hills
and the project area has also heen included in the development costs of the scheme,
since these hills form the nearest available source of rock material for construction
purposes. Hence, only the extension of this link to the existing Hairobi-Garissa
road has been excluded from the development costs. It is considered that this link
would be provided from general government expenditure on roads, as required and
justified by the volume of traffic to be carried.
Discussion with the Ministry of Works, Communications and Power indicated
that the realignment of the Hairobi-Garissa road would not seriously inconvenience
persons travelling beyond the project area to the hinterland of the northern Frontier
District. Obviously, most of the development of that district will be restricted
by lack of adequate rainfall. Managed rangeland will be the major use of the area.
Access for delivery of cattle to coastal, interior and project markets would be
substantially improved through the new access links to Mombasa and Nairobi via
the Korokora diversion dam.
/
13,5 N Korokora Dam
As has been shown in Chapter XI, the development of power generation on the
middle reaches of the Tana will involve regulation of the natural flows to more or less
steady flows below Koreh. The fluctuating seasonal demands of irrigation call for these
steady flows to be re-regulated to correspond with these demands. Thus provision of
a re-regulating reservoir at Korokora forms an essential item in the development of the
full potential area of irrigation. In Section K 13.5 of Technical Volumeyi (Appendix
K), the design of the dam at Korokora is discussed in detail. On Plate 18, the
general arrangement of this work is shown. The capital cost of the dam and headworks
is estimated to be S.A. £ 11,040,000.
I3.6 Capital Costs - Irrigation Development
Table 13-2 gives summarised estimates of the capital costs of all items
comprised in the irrigation development, in two forms. The first form shows the
original estimates framed in the studies made for the project) the ultimate total,
for a potential area of 300,000 acres, is some £ E.A. 60,000,000. The seoond form
gives a tentative forecast of the reduced costs that may result if roads within the
scheme are merely earth roads throughout, unpaved. For this the ultimate total is
forecast as some E.A. £ 47,000,000,which is equivalent to an over-all rate of some
E.A. £ I57 per acre. It should be noted that the figure0 corresponding to the first
f era are used in the full economio evaluations discussed in Chapter XV".

! rWtm (MM*
If, Jrt
JMU ««•»?«•
jpmmza&enai
£^k i&Ë$L
SECTION E - E
SIMVEV OF IRRIGATION POTENTIAL
LOWCR TANA HIVCH IM«
jron» urn MM njiaji I'IUTHI»! w _ni apTOMni
DISTRIBUTION SYSTEM
LAYOUT OF IRRIGATION BLOCK
AND TYPICAL SECTIONS .
PLATE IT

13.7 Research and TVajsis^ Pontic
-116-
As a result of the project studies made, it is suggested that,as an integral
part of irrigation development, there is a need for continuous agronomic research
into new crops, fertilisers, insecticides, farm machinery, and so on* There is also
a need, during the period of development, to train agricultural staff, and cultivators.
To meet these needs, -it is proposed to set up a permanent Eesearch and Training Centre
under the Irrigation Authority which would be responsible for the whole scheme. It
is contemplated that an area of some 8,300 acres would be suitable for this purpose,
to be located so that the soils in it should be reasonably representative of the major
types to be found in the scheme area, and also so that it should be fairly centrally
sited in the northern part of the area, which would be the first part to be developed.
Close to the Centre could alBO be the site for the headquarters of the Authority,
and the local administrative offices of the central government, envisaged as being in
a township area of some 700 acres. The whole is proposed to be sited near the Tana
river and south of the Lugga Hiraman.
To make the Centre available quickly and avoid the need to await the completion
of the Korokora Sam and the main canal from it, it is proposed that a pumped water
supply be provided to be taken from the Tana river at a suitable point and conveyed
in a special canal on an alignment different from that of the ultimate main canal.
Particulars of the layout and estimated costs of the Research and Training
Centre are given in Technical VolumeVI - Appendix L. The costs are here summarised
in Table 13-3, totalling some E.A. £ 2,915,000.
13,8 Pilot Scheme - First Stage of Development
It is considered that a first development as that proposed for the Centre
should from the first be regarded as a pilot scheme, primarily for production,
rather than as merely a centre for training and research. Part of the area should
be set aside for research and testing) the rest should be operated primarily for
production, to be combined with "in-service" training and experience for all
concerned, from managers down to cultivators and subordinate staff. Initial
development such as this would need at most some 150 cusecs of water, out of the 1,100
cusecs minimun flow available in the river under natural conditions, i.e. before
the completion and operation of upstream storage reservoirs for power generation.
The need for the Korokora Dam, to obtain command of the ultimate proposed main canal,
and to provide storage oapacity for re-regulation to suit the incidence of irrigation
needs, oould be deferred until a decision could be reached in the light of aotual
experience of results from this first initial development.

Tebls 13-
Item
-118-
Zatimates of Capital Costs-Irrigation Development
Estimate of oost
using
paved roads
£ E.A.
Korokora diversion dam 11.040.000
Main canal 5.450.000
Section-feeder canals 2,476,000
Night-storage reservoirs 429*000
Block-feeder oanals 2,665,000
Unit-feeder canals 257,000
Drainage 1.280.000
Internal roads 7»561,000
Ploodplain lands 1,040,000
Land clearing and levelling 3.962.000
Subtotal for 136,000 acres north of L. Thowa
add costs of 114,000 sores south of L. Thowa
Hain canal extension 1,107,000
Irrigation and drainage 5»974»000
Internal roads c= 6,509,000
Land olearing and levelling 3.321.000
Subtotal for 250,000 acres irrigation
development
A.dd costs of additional 50,000 acres south
of L. Thova:
Ilain canal extension
100,000
Irrigation and drainage 2,620,000
Internal roads 2,855,000
Land clearing and levelling 1.457.000
Srand total - 300,000 acre irrigation
development
£ E.A.
11,040,000
5,450,000
7,127,000
12.563.000
36,180,000
16.911.000
53,091,000
71032,000
£60.123.000
Estimate of cost
using
earth roads
£ E.A. £ E.A.
11.040.000 11,040,000
5.450.000 5,450,000
2,476,000
429,000
2,685,000
257,000
1.280.000 7,127,000
2,000,000
1,040,000
3.962.000 7.002.000
30,619,000
1,107,000
5,974,000
1,400,000
3.321.000 11.802.000
42,421,000
100,000
2,620,000
615,000
1.457.000 4,792,000
£47.213.000

-119-
Table 13-3 Research and Training Centre - Estimate of Capital Cost
Item
Temporary water supply system:
Pumping station
Conveyance canals
Research facilities!
Offices, laboratories,
workshops, housing, etc.
Training facilities:
Offices, housing, transport,, etc.
Total additional costs of Research
and training centre
Irrigation development (as included
in totals presented in Table 13-2):
Irrigation, drainage and road
networks
Land clearing and levelling
Floodplain lands
Total development cost of Research
uii Training Centre
176,000
254.000
1,159,000
242,000
34.000
430,000
400,000
650,000
1,480,000
1,435,000
£ 2,915,000

14 »1 Genexaj-,
-120-
INFRASTRUCTURE AND SECONDARY DEVELOPMENT
CHAPTER "XIV
The development of irrigation on a large scale on the almost uninhabited
lowland plains of the Tana basin will necessitate very substantial investments
in institutional and social infrastructure, in addition to the works involved on
the irrigation network and processing plants. While such infrastructural investments
are not considered in the evaluation of the economic viability of irrigation
development as such, it is apparent that they must be taken into account in an
over-all appraisal» Hence, although it was beyond the scope of the studies made for the
project to detail a comprehensive plan for the over-all development, a preliminary
assessment of basic infrastructural requirements was made to provide at least some
indication of the order of magnitude of the investments involved. The discussion of
infrastructure, secondary developments and sociologie implications is contained in
Technical Volume VII (Appendix M).
The basic infrastructure there considered included such items as external road
communications, townsites and service, tenant housing and general government
administration. In addition, local secondary developments such as forestry and inland
fisheries, which might be justified to provide the scheme population with part of their
food and fuel requirements, were given preliminary consideration. Certain aspects
of such secondary development are discussed briefly here, as is the potential hazard
of a conflict between wildlife and agricultural development within the lower basin.
The social implications of development are discusssd only to indicate the special
conditions which could ar-iee through the resettlement of a large population in an.
isolated area and to suggest the need for timely studies to determine what provisions
would be required to meet the demands of health, education and other social services.

-121-
The population ultimately to he settled in the scheme area will consist
largely of tenants and other agricultural workers and their families. These would
all he directly associated with the primary production of crops and are "estimated to
numher between 400,000 and 500,000 persons, assuming an average of five persons per
family. In addition, it has heen assumed that government transportation services and
other activities would provide employment opportunities for a further 25,000 to 30,000
workers and thereby increase the population by between 100,000 and 150,000 people.
While admittedly approximate, it appears reasonable to envisage an ultimate population
of some 500,000 to 600,000 people, directly supported by the ultimate irrigation
development.
14.2 Requirements
The functional requirements of the irrigation system and the layout of irrigable
lands dictate to a great extent the pattern of social development and land use.
Although only some 300,000 acres of land are considered to be irrigable, it must be •
noted that this is a net acreage and that, in addition, a substantial part of the
project area would be occupied by canals, drains, roads and townsites. Nevertheless,
about half of the project area would remain unproductive, either through lack of
water or because of inherently unfavourable topographic and soil characteristics.
The administrative and institutional organization therefore must be planned for an
ultimate 'population of over half a million people, spread out across an irrigation
complex occupying more than one million acres of land.
From the point of view of scheme management and from considerations of the level
of social service desirable, it is understood that the Government of Kenya, through
the Tana Steering Committee,wishes planning to provide.for settlement of the farming
population in rural communities, each of which is expected to serve an irrigation
subdistrict of approximately 10,000 acres.
As described in Technical Volume VII (Appendix M), communities have been envisaged
as groupings of village units around a town centre in which the social amenities and
general services necessary to support community living would be provided. The level
of services and standards of construction as proposed therein were reviewed with the
Tana Steering Committee to ensure that they conform to Government policy.
Cost estimates were prepared for townsite development and services and for housing
for communities of two sizes, for 12,000 and 25,000 people. Over-rail, these work out
approximately as follows:
Townsite development and Services 90 )
Housing 110 )E.A. £/head
£ 200 )

-122-
For a total porulaticn assumed to he 500,000, in a scheme of 250,000 net
irrigahle acres, this is equivalent to £400 per net acre. Investments for commercial .
or private enterprises, or for processing industries, are not included in this
already formidable figure.
Communications will also he an important aspect of development. Road connections
have heen proposed throughout. The internal road network and the external links
to Mombasa and Nairobi have heen discussed in Chapter £111, where it is noted that the"cost
of both the internal roads and of the quarry road to the Kandelongwe Hills are
assumed to form part of the direct investment in irrigation. Of the external roads,
the cost of the link to Nairobi was not estimated, the cost of the surface trunk
road from the scheme to Mombasa was estimated to he nearly E.A. £ 8.5 million.
The cost of other facilities for communication, such as airstrips, and telephone
and telegraph service, were not estimated in the studies. It appears obvious that
an airstrip will be essential, but it is for the Government to consider on what
standard provision should he made. From experience of large and intensive irrigation
schemes elsewhere, a comprehensive telephone service throughout the irrigable area
and to all important points such as headworks is quite essential, for purposes of water
control, management, and agricultural administration; otherwise the standard of
efficiency requisite for economic viability is unattainable. This service can
probably best be provided and operated as part of the national telephone service, at
standard charges.
It is recognised that there are special health hazards involved in the use of
irrigation in the tropics. For development in the lower Tana, these were assessed
by a WHO mission, the results of which are included in Technical Volume VII
(Appendix M). It is therefore recommended that adequate standards of water supply
and of sewage disposal, appropriate to the local conditions, should be provided.
In the figure of £ 90 per head, mentioned above as the estimated cost of townsite
development and services, the studies, may \ appear to have allowed for water-borne
sanitation for sewage disposal. For the local conditions, certainly in the early
stages of development, this seems unnecessary) various other methods have been used
elsewhere with acceptable results. Certainly this and other items of expenditure
involved in the provision of the infrastructure should be most carefully scrutinised '
before they are adopted for development.
/
14.3 Other Aspects
In Technical Volume .vfI (Appendix M) is included a preliminary report on the
fisheries potential of the Tana river, as it is at present, and as it is foreseen
when the reservoirs envisaged provide new sources for inland fisheries. The opinion
was expressed that the various dams would be unlikely to have significant adverse
effects on migratory fish, and that in the new reservoirs, species of commercial
interest would become established and make possible considerable increased production.
In the same,volume there is a report on the possibility of conflict between
agriculture and elephants, in the lower Tana Irrigation scheme. The conclusion
\ reached is that there is little likehood of this. Changing ecological conditions
have resulted in the desertion of the area by most of the former game population.
However, it is recommended that control measures be planned by the"Game Department
of Kenya, so that they can be applied if occasion should arise.

-123-
Also considered in the same, volume is the potential of the flood-plain of the.
Tana river and other limited areas of the scheme, for the development of forestry*
Little is at present known about this, in this area, and it is recommended that
experimental work be undertaken to determine what species óf trees would be best
suited to the local conditions. If successful, well-managed forests could supply
a large part of the local demands for fuel and rough timber, and also provide additional
employment,
14 »4 Processing
This has already been briefly discussed in Chapter IX. It is mentioned here
again, since the provision of processing plants can approximately be inoluded in the
picture with that of Infrastructure. The items considered inoluded pressing and
refining of sugar, ginning of seed cotton, pressing of cotton seed and other oil seeds
for oil, and converting kenaf into bags. In the studies made, details of the factories
and equipment required were not worked out; but for an ultimate developed area of
250,000 acres, an over-all figure of £40,000,000 was envisaged as investment cost..
If, as is now suggested, the cropping pattern is modified, some of these items may be
reduced in magnitude, or even eliminated. For the present, however, it may be
suitable, to assume this figure of cost tentatively, until the picture can be further
olarified.

15«1 General
-124-
ORGANIZATION AND MANAGEMENT
CHAPTER XV
The area of the scheme is remote, and at present sparsely populated* To
attract settlers there, the social and personal economic factors are of prime
importance* Living conditions and amenities, marketing arrangements, conditions
of tenancy and land tenure, and above all, financial returns to the individual
cultivator, are at least as important as, if not more so,than cropping patterns
and questions of agricultural technique.
An adequate return on the high rate of investment required for the development
of irrigation can only be aohieved with high standards of husbandry and
production. To ensure these, the whole development and its management should be
in the charge of a semi-autonomous "Gezira ,, -type organization, to be called the
"Tana River Irrigation Authority". This would be responsible for the construction
and operation of the scheme, as well as for the marketing of produce* It should
also undertake research, the training of staff and cultivators, and the organization
services, with the control of secondary agricultural activities suoh as
forestry. It might well also own and operate processing plants. Por the work of
development, including land clearance, levelling and the construction of distributory
canals, it would have to maintain quite a large construction force ; it might
then undertake also the construction of publio faoilities such as cultivators*
housing* It is stressed that the only effective means of seouring the requisite
standards of efficiency is through such an Authority.
Furthermore the whole organization of the scheme, including cropping patterns,
conditions of tenancy and of cultivation, financial arrangements at all
levels, relations between Government, Authority, and cultivators, and all the
other points which will be involved in development, in operation ' and management,
should at first be defined and agreed upon by all concerned. When this has been
done, the arrangements should be applied and tested on a first development of
modest but adequate size, so that any adjustments suggested by actual experience
can be made, before full-scale development is undertaken.

15.2 Specific Points
-125-
There is no doubt that many of the technologic and managerial skills required
during the initial years of construction and development of such a large complex
will have to be imported* At the same time, provision must be made to train Kenya
citizens in the management and administrative aspects of the scheme.
Infrastructural development will need to be closely, controlled and scheduled
to remain in balance with the construction of productive facilities. Hence, a
strong case can be made for utilizing the construction forces of the Authority to
oversee the construction of all physical facilities and installations required
within the project area.
A schematic organization chart, indicating the primary functions of an
Authority such as has been discussed herein, is presented on Plate 19. Therein,
it may be noted that operations are divided between agricultural management and
engineering, whilst construction forms a special division of the engineering arm.
The agricultural division of the Authority would be concerned with the
provision of research facilities, supervision and training of tenant farmers, and
with marketing and related functions. The engineering division would be responsible
for water control and the scheduling of irrigation deliveries, as well as the
construction of all physical works and installations, and the maintenance and operation
of mechanical plant and construction equipment.
Within the headquarters administration, a tenant affairs section has been
suggested to deal with grievances and suggestions which, no doubt, will, arise as à
consequence of the natural aspirations of the tenants for an increasing -voice in the
operation of the scheme as time goes by. Details have not been considered at
present} however, it is suggested that, as early as possible, tenants should be given
some degree of self-government at the village level. As their experience increases,
they might well be asked to participate, through co-operatives, in operating mechanical
plant in their own districts and in supervising various other community
activities. Much can be learned from the history of social and political development
in the Gezira scheme in the Sudan.
Although it is not appropriate at this time to oonsider these matters in ,
great detail, it is apparent that the proper organization and administration of the
scheme will be.fundamental to its success. For the purposes of this report, a Tana
River Irrigation Authority has served as the model for estimating the costs of
operation, and as the appropriate level from which to view the economic evaluation
of development. Whatever form of organization is ultimately adopted, the funotions
and number of staff required, as well as the essential costs of operation and
maintenance of the development, will be more or less the same.

DEPUTY GENERAL MANAIIER
OPERATIONS
• •••ARCH ANO
DEVELOPMENT
E
SECTION I
SECTION MANAMA (A.0.1
M.000 ACRES
I AMt CANAL SUPT.
IS WATER GUARDS
I AGST. A a'S
IRRIGATION UNIT-IOOO AC
A.F.A.
I HEAD CULTIVATOR TO
EVERY IRRIGATION SUS UNIT
ACCOUNT!
AMICULTURAL
OIVItlON
c iMSTMCT MANAGER ISCAJOJ
10,000 ACRES
CJMAL SUPERINTENDENT
CAN AL MEAOWORK OR STAFF
C'HAL MAINTENANCE STAFF
AI ST MST. MANAGERISP.AXU
S >k.a SPECIALISTS
I WORKSHOP SUPT.
NATIONAL IRRIGATION BOARD
GENERAL MANAGER
DEPUTY OINENAL. MANAGER
ADMIN. ANO FINANCE
LOCAL GOVERNMENT
ADVISORY COMMITTEE
ZL.
TENAIT'
ADVISORY COMIIITTtl
MARKETING PERSONNEL PURCHASING STORES TENANT AFFAIR!
EXTENSION AMI EDUCATION
ITIAMMOf TECHNICAL STA«
ANO TENANT»)
ISLOCK t I SLOCKÎ BLOCK 4
OISTRICT MANAGEMENT
ANO OPERATION
SECTION MANAGEMENT
AND OPERATION
UNIT MANAGEMENT
AND OPERATION
OPERATION AND
MAINTENANCE
ENGINEERING
DIVISION
CONSTRUCTION ]
S
M
I
e
«
GOVERNMENT OF KENIA
UNITED NATIONS SPECIAL FUND
SURVEY OF IRRIGATION POTENTIAL
LOWER TANA RIVER BASIN
FMO AH MMCUITUK OMAMUTlOa OF TKt UHTtS MTOa
IRRIGATION PROJECT
SCHEMATIC MANAGEMENT
ORGANIZATION CHAITT

- 127 -
ECONOMIC EVALUATION
CHAPTER XVI
In the studies made under the project to evaluate the economic aspects of projeot
development, the discounted cash flow method of analysis was adopted. The advantages
of the method are that it not only eliminates problems of selecting suitable interest
rates, but usually also provides a more explicit answer than other methods, especially
at the national planning level when comparisons have to be made with other projects
whioh oompete for limited development funds. The method results in streams of investments,
annual costs and benefits, and leads to an internal rate of return.
This evaluation was made for two stages of project development. First,the
irrigation development alone and, secondly, the irrigation project together with
certain processing activities included. The streams were assumed to originate from
and accrue to a Tana Irrigation Scheme Authority.
The investment and oost streams include only those expenses which are directly
attributable to the project or form imputable indireot costs, such as maintenance of
the trunk road between the project area and Mombasa during an initial period. The
benefit streams inolude the values of production, at farm level and ex-processing
factory respectively, after deduction of costs for inputs such as fertilizers, fuel,
spare parts and skilled labour. Farmers' labour and unskilled labour employed in the
processing industries are considered to have zero return opportunity and are therefore
not oounted as a cost. Their remuneration is still included in the project benefits,
so that the internal rates of return obtained provide an indication of the profitability
of the projeot to the national economy.
To complete the economic picture, an approximate schematio finanoial analysis
was made which took into account all the actual expenses of the authority, including
those to farmers and unskilled labourers. The purpose of this assessment was to illustrate
the order of magnitude of the funds required annually during the first
period when expenses still exoeed proceeds, and what types of loans might suit best
in financing the projeot, taking into aocount the positive balance of proceeds over
expenditures during the seoond part of the theoretical lifespan of the project.
Finally, some comments were inoluded on the foreign currency aspect of the
project.

16.1 Internal Rates of Return
Irrigation development
-128-
The various cash flows were based on the following considerations and assumptions»
together with the costs and benefits derived in previous sections of this report«
(a) For each of the two levels of development, 250,000 and 300,000 acres,
two rates of development were assumed. Rate 1 envisaged, after an
initial period, a uniform development of 10,000 acres of newly reclaimed
land per year, as discussed in Chapter,XI.
(b) The time required for construction and land reclamation would be
between 20 and 30 years, depending on the size and development rate
of the scheme« In accordance with current practice of such agencies
as the International Bank for Reconstruction and Development, the
economic analyses were made for a period of 50 years, even though
the useful physical life of well-maintained works would be much longer.
Although reinvestments in plant and maintenancetcosts of works would
continue, as discussed in Chapters XII and XIII effective water control
could be foreseen for 100 years or more from the power complex and the
Korokora diversion dam, and hence no major reinvestments in works for
water control nor irrigation are foreseen within practical limits of
economic evaluation.
(c) The land would be cleared two years before it is taken into production,
so that the irrigation and drainage canals and internal roads could be
constructed and the farm land levelled in the remaining year before
cultivation started.
(d) The on-farm investments and reinvestments included the cost of initially
supplying each new farmer with irrigation siphons, working capital and
consumptive credit. Further, they comprised the purchase and regular
replacement of agricultural machinery, estimated to cost about £ 2,000
per unit including implements, and the installation of workships for
maintenance and repair of the fleet of machinery.
(e) Farm income, before payment of any land and water charges, would start
at a level of t 47.50 per aore and increase gradually as explained in
Technical Volume V, Section H9.5.5 °* Appendix H. The improvement was
taken to be equivalent to a compounded annual increase of one percent
over the basio level. Further, it was assumed that only 75 sLaà $0
percent respectively of the yield level, at that time, would be obtained
during the first two year» of cultivation on newly reclaimed land«
(f) The on-farm costs, which were subtracted from the gross value of
produce to obtain farm income, included such items as interest on
credit and charges for mechanization services. In order to be consistent,
these costs had to be considered as income or revenue to the
authority which would provide these services. The apparent profit
on training of new farmers has also been considered as a revenue in
the cash flow.

COL.
Y
E
. TABLE.I6-IA
INVESTMENTS FOR IRRIGATION DEVELOPMENT
RATE I - 250,000. ACRES
£ x 1,000
3. 5.
MAIN CANAL,
IRRIGATION/DRAINAGE
TWORARY SYSTEM,*
A WATER SUPPLY INTERNAL ROAOS, RESEARCH ON-FARM
R RESEARCH ANDTRAININ6 HEADQUARTERS AND INVESTMENTS
QUARRY ROAD" CENTRE KORWOM DAM AND SCHEME TRAINING CENTRE AND RE-INVESTMENTS TOTAL
1 1,044 83 32 1,159
•2 347 1,06« 705 239 9 2, «5
3 2,128 1,259 300 13 3,700
4' • DISLOCATION
ALLOWANCE
2.128 1,998 360 23 4,509
s\- 300 2,660 3,126 40 45 6,171
s -.'' «-.••'-ja» -f.-;. r . -:' ' 45 . 2.660 1,612 40 445 5.102
5.:'• 1,736 40 453 2,229
8 1,644 40 157 a;«i
••:»• '••>' '• ""• ' ' • • ' ' • 1,813 465 2,278
lb 1,777 485 2,262
n 1,725 485 2.2IÖ
12 1,507 493 2,000
13 1,508 497 2,005
14 1,555 505 2,060
15 1,728 525 2,253
16 1,851 525 2,376
17 2,159 533 2,682
18 1,516 537 2,053
19 1,561 545 2,106
20 1,446 566 2,011
21 1,445 566 2,0 tO
22 1,447 573 2,020
23 1,472 577 2,049
2» 1,48« 585 2,071
25 1,514 605 2,119
26 1,446 606 2,051
27 1,446 613 2,059
28 1,286 617 1,903
29 580 580
30 600 600
31 200 200
32 200 200
33 200 200
3i| 200 200
35 200 200
36 290 290
37 290 290
38 200 290
39 200 200
40 200 200
HI 200 200
42 200 290
43 290 200
14 200 290
45 200 • 290
46 200 290
47 200 390
48 200 200
49 290 290
50 200 200
TOTAL
1,044
600
* INCLUDING CLEARING AND LEVELLING
475 ».« 43,800 1,050 17,525 75.134

COL. I.
TABLE 16-1B
INVESTMENTS FOR IRRIGATION DEVELOPMENT
RATE 2 - 250,000 ACRES
£ x 1,000
2. 3. ». 5.
Y
MAIN CANAL.
IRRIGATION/DRAINAGE
E TEMPORARY SYSTEM,
A MTER SUPPLY INTERNAL ROADS, RESEARCH ON-FARM
R RESEARCH AND TRAINING HEADQUARTERS AND INVESTMENTS
QUARRY ROAD
CENTRE KOROWRA DAM
AND SCHEME TRAINING CENTRE AND RE-INVESTMENTS TOTAL
1
1,044 83
32
1.159
2 347 1.064 705 230 9 2,355
3 2.128 1.259 300 13 3.700
4 DISLOCATION
2.128. 1.998 360 .23 4.509
ALLOWANCE
5 300 2,660 3.126 40 45 6.171
6 300 45 2,660 1.666 40 445 5,156
7 1,899 40 453 2,392
8 2.567 365 479 3.411
9 2,530 488 3,018
10 2.479 707 3.186
II 2,309 708 3,017
12 2.S62 715 3,277
13 3.404 325 762 4,491
m 3.599 770 4,369
IS 3.034 990 4.024
16 2.933 990 3,923
17 2,959 998 3,957
18 2,813 .042 3,855
19 1.928 .028 2,956
20 980 980
21 780 780
22 200 200
23 200 200
24 200 200
25
200 200
26 200 200
27 200 200.
28
200 200
29
200 200
30
200 200
31
200 200
32
33
34
35
36
37
38
200
200
200
200
200
200
200
200
200
200
200
200
200
200
39
200 200
200 200
11
200 200
H2
200 200
13
44
15
46
17
48
49
50
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
200
TOTAL
,044
600
475 .43,802 1.700 18.225 76.486

TABLE 16-IC
INVESTMENTS FOR IRRIGATION DEVELOPMENT
RATE I - 300,000 ACRES
£ x 1,000
COL. I. 2. 3. ». 5. 6. 7.
*
Y
MAIN CANAL,
IRRIGATION/OMUIASE
E TEMPORARY SYSTEM,
A
WATER SUPPLY
RESEARCH AND TRAINING
INTERNAL ROADS,
HEADQUARTERS
RESEARCH
AND
0N-FAB4
INVESTMENTS
R QUARRY ROAO
CENTRE icOROKOJU DAM AND SCHEME TMIRIN6 CENTRE AND RE-INVESTMENTS TOTAL
1
1,044 83 32 1,159
2 347 1,084 70S 230 9 2,355
3 2.128 1,259 300 13 3.700
4 DISLOCATION
ALLOWANCE
2,128 1,998 380 23 4,50»
5 300 2.6» 3,126 40 45 6,171
6 300 45 2,660 1.612 40 445 5,102
7 1.736 40 453 2.229
B 1,6*4 40 457 2,141
9 1,613 465 2,278
10 1,777 485 2,262
II 1,725 48S 2,210
12 1,507 493 2.000
13 1.508 497 2,005
14 1,556 505 2,060
ts 1,726 525 2.253
16 1,651 525 2,376
17 2,159 533 2,692
18 1,516 537 2.053
19 1,561 545 2,106
20 1,446 565 2,011
21 1,445 565 2,010
22 1,467 573 2.020
23 1,472 577 2.049
2* 1,466 565 2,071
25 1.514 605 2.119
26 1,446 60S 2.051
27 1,466 613 2,079
28 1,476 617 2.093
29 1,466 625 2,120
30 1,447 645 2.092
31 1,445 645 2,090
32 1,446 663 2,099
33 1,266 657 1,943
34 620 620
35 640 640
36 240 240
37 240 240
38 240 240
39 240 240
40 240 240
«1 240 240
42 240 240
43 240 240
m 240 240
«5 240 240
46 240 240
47 240 240
48 240 240
49 240 240
50 240 240
TOTAL I.» 1 » 475 10.640 61,129 1.060 20.430 66.368

COL.
TABLE 16-ID
INVESTMENTS FOR IRRIGATION DEVELOPMENT
RATE 2 - 300,000 ACRES
£ x 1,000
6. 7.
Y
WIN CANAL,
IRRIQATION/DRAIIUGE
E TEMPORARY SYSTEM,
MATER SUPPLY INTERNAL ROADS, RESEARCH ON-FARM
A RESEARCH AND TUININB NEAOOVA«TERS AW INVESTMENTS
R QUARRY ROAD . ... CENTRE MO SCHBC TRAINIM CENTRE AW RE-INVESTMENTS TOTAL
1
1.044 83 32 1,159
2 347 1,06» 705 2*0 9 2.355
3 2,12» 1.25« 300 13 3,700
i» DISLOCATION
ALLOWANCE
2,128 ' I.SM 3« 23 ' 4,509
5 300 2,80) 3,126 40 '45 6,171
6 300 45 2,6*0 1,666 no 446 5,156
7 *. r" l,*M 40 453 2,392
8 2,567 365 479 3,411
9 2,530 488 3,018
10
M
12 2,562 715 3,277
13 3,Mm 325 762 4,491
m 3,509 770 4,369
15 3.0» 990 4.024
16 2,933 990 3,923
17- - 2,959 968 3,957
18 2,913 1,042 3,955
19 2,921 1,050 3,971
20 ** 3,023 1,070 4,093
21 1,215 1,093 4,308
22 1,9» 1,040
23 1.240 1.240
24 240 240
25 240 240
26 240 240
27 240 240
28 240 240
29 240 240
30 240 240
31 : - 240 240
32 2*0 240
33 240 240
3>» 240 240
35 240 240
36 240 240
37 240 240
38 240 240
39 240 240
MO 240 '40
41 240 240
12 240 240
u 3
44
»5 240 240
46 240 240
47 240 240
48 2H0 240
19 240 240
50 240 240
TOTAL 1.044 475 10.« 54,133 1,700 21,610 87,202
2,479
2,309
707
703
240
240
3,186
3.017
240
240

COL.
TABLE 16-2A
IRRIGATION DEVELOPMENT - ANNUAL COSTS AND BENEFITS
RATE I - 250,000 ACRES
£ x I,000
2. 3. ». - 5.
MANAGEMENT AUTHORITY,
Y RESEARCH TRAINING
E OPERATION ANO CENTRE.
COSTS BENEFITS
A HAINTENANCE- HEADQUARTERS AND SCHEME, REVENUES TO
MAINTENANCE OF OAM, IRRIGATION/ ANO OPERATION AUTHORITY FROM
R QUARRY ANO DRAINAGE SYSTEM, AND MAINTENANCE. NET VALUE OF TRAINING, CREDIT
TRUNK ROAD' ANO ROADS OF MACHINERY TOTAL FARM PRODUCTION AND MACHINERY TOTAL
1 m
14
2 37 119 156
3 37 22 241 300 40 40
4 '37 62 303 402 100 100
5
6
. 331»
33*
1»
250
370
398
828
982
' '
356
200
248
200
604
7 334 376 4SI 1.191 792 296 1,088
8 334 427 563 1,324 1.284 344 1,628
9 331» 171» 615 1,423 1,786 392 2.178
10 331» 528 668 1.530 2.298 440 2,738
II 334 580 720 1.634 2.820 488 3.308
!2 334 630 773 1.737 3.353 536 3.889
13 33» 672 825 1.831 3.895 5«4 4.479
It
IS
16 "
17 '
18
19 '
20
21
22
23
ri
25
26
27
28
29
30
31
32
334
37
18
7Î5
'759
809
864
929
972
1,017
1.057
1.098
1.138
1.179 -
1.221
1.26«
1.304
1.345
1.385
1.385
1.385
1.385
'878
927
976
I.02S
l;074
1.123
1.172
1.221
1.270
1.319
1.368
1,417
1.466
1.515
1,56»
1,613
1.613
1,613
1.613
1,927
1.723
1.803
1.869
2.003
2.095
2.189
2,278
2.366
2,457
2.547
2.638
2.730
2.819
2.909
2,998
2.998
2,9*8
2.998
4.449
5.012
5.587
6.172
6.769
•7,378
7,997
8.629
9.272
9.928
10.595
11.275
»1.967
12,672
13.391-
14.121
14,86«
15,167
15.380
632
680
728
776
824
872
920
968
1.016
1.064
1.112
1.160
1.206
1.256
1.304
1.352
1.200
1.200
1.200
5.081
5.692
6.315
6,948
7,593
8.250
8.917
9,597
10.288
10.992
H.707
12.435
13.175
13.928
14,695
15.473
16,066
16,367
16,560 :
33
34
35
36
37'
38
39
40
41
42
43
'14
45 .
•tc
47
48.
49
50
1,385
1,385
1.385
1.385
1.385
1.385
1.385
1,385
1,385
1.385
1.385
1.385
1.385
1,385
1.385
1.386
1,385
1,385
1.613
1.613
1.613
1,613
1,613
1.613
1.613
1.613
1.613
1.613
1,613
1,613
1.613
1,613
1,613
1,613
1,613
1,613
2.998
2.998
2.998
2.998
2.998
2.998
2.998
2.998
2.998
2.988
2,998
2.998
2.998
2,99«
2.998
2.998
2,999
2.998
15,535
15.690
15.848
16.005
16.166
16,326
16.490
16.655
16,823
16.990
17,160
17.333
17,055
17.680
17.658
18,036
18,215
18.398
1.200
1,200
1.200
1.200
1.200
1.200
1.200
1.200
1.200
1.200
1.200
1.200
1.200
1.200
1,200
1.200
1.200
1,200
16.735
16.890
17.048
17.205
17.365
17.528
17.680
17.855
18.023
18.190
18,360
18,533
18.705
18.880
19.059
19.236
19,415
19.598
TOTAL 3.506 50,286 59.891 113,603 511,924 44.740 556.664

COL.
TABLE I6-2B
IRRIGATION DEVELOPMENT - ANNUAL COSTS AND BENEFITS
RATE 2 - 250,000 ACRES
t x 1.000
2. 3. H. 5. 6.
COSTS BENEFITS
Y
MANAGEMENT AUTHORITY,
RESEARCH TRAINING
OPERATION AMD
CENTRE,
E NAINTEMNCE- HEADQUARTERS AND SCHEME, REVENUES TO
A HilRTEN/UKE OF .DAM, IRRIGATION/ AND OPERATION AUTHORITY FROM
R QUARRY AND DRAINAGE ÏYST94, AND MAINTENANCE NET VALUE OF TRAINING, CREDIT
TRUNK ROAD .
AND ROAOS OF MACHINERY TOTAL FARM fRODUCTION AND MACHINERY
TOTAL
1
1«
14
2 37 119 156
3 37 22 241 300 40 40
4 37 62 303 402 100 100
5 331 124 370 828 200 200
6 334 250 398 982 356 218 604
7 331 378 484 1.196 792 296 1.088
8 33« 432 570 1,336 1.284 344 1.628
9 334 506 647 1,487 1,786 492 2.278
10 331 580 724 1.638 2.484 •564 1.018'
II 331 661 801 1.786 3.232 c.36 J. 666
12 334 717 878 1,929 4.021 708 4.729
13 18 788 952 1,756 4,825 780 5,605
n 887 1.060 1,937 5,644 952 6.596
15
16
17
18
19
20
2<
22
23
21
25
26
27
28
29
30
31
32
33
3«
35
36
37
38
39
«O
«1
12
«3
45
16
17
18
19
50
993
1.078
1,161
1,244
1.325
1.385
1,385
1,385
1.365
1,385
1,385
1,385
1,385
1,386
1,385
1,386
1,385
1,385
1,885
1,385
1,385
1,185
1,385
1,385
1,385
1,385
1,385
1,386
1.385
1,385
1.385
1.385
1,385
1.385
1.385
1.148
1.246
1,344
1,442
1,540
1,613
1,613
1,613
1,613
1,613
MI3
1,613
1,613
1,613
1.613
1.613
1,613
1,613
1,613
1.613
1,613
1,613
1.613
1,613
1.613
1,613
1,613
1.613
1.613
1.613
1,613
1,613
1.813
1,613
1,613
1.613
2,141
2,324
2.506
2,686
2.866
2.998
2,998
2,998
2,998
2,998
2,998
2,998
2.9*8
2,998
2.998
2,998
2.998
2.998
2,998
2,998
2,998
2.998
2,998
2,998
2.998
2,998
2.998
• M«
2,998
2.998
2.998
2.998
2.998
2.998
2.998
2.998
6.674
7.764
6,901
10.060
11.242
12,447
13.399
13,811
14.063
- 14.203
14.345
14.488
14.633
14,780
14.928
15.078
15,228
15,380
15.535
15,690
15.846
16.005
16,166
16.328
16,490
16,655
16.823
16.990
17.160
17.333
17,505
17,680
17.858
18.035
16.215
18.398
.048
1,144
1,240
1.336
1.432
1.428
1,200
1.200
1.200
1,200
!.200
. 1.200
1.200
1.200
i.200
1.200
1.200
1.200
1.200
1.200
'.200
1,200
1.200
1.200
1.200
.200
1

COL.
i
2
.3
4
5
6
7
8
9
10
II
12
13
14
IS
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
MAINTENANCE OF
QUARRY AMD
TRUNK ROAD
37
37
37
334
334
334
334
334
334
334
334
334
334
37
18
TABLE I6-2C
IRRIGATION DEVELOPMENT -ANNUAL COSTS AND BENEFITS
RATE I - 300.000 ACRES
£ x 1,000
2. 3. "»• 5. 6.
COSTS
MANAGEMENT AUTHORITY,
RE3EARU TUINIM
OPERATION AMD CtRTM,
MAINTENANCE- HEAOOUUTEM AND SCJEME,
DAN, IRRIGATION/ AND OPERATION
DRAINAGE SYSTEM, AND MAINTENANCE
' AMD ROADS Of MACHINERY
22
IN
119
»1
62
303
12«
370
250 398
376 «II
427
5«3
474 6IS
528 6«
580
7»
630 773
672
825
715
•78
759
927
809 976
864
1,025
92»
1.074
972
1.123
1,017
1.172
1,057 1.221
1,098
1.270
1,138
1.319
1,179
1.368
1,221
1,417
1,264
1,466
1.304
1.515
1,345
1,564
1,387
1,613
1,429
1,662
1.469
1.711
1,510
1.760
1,550
1,809
1,591 1,85«
1.591
1,858
1,591
1,858
1,591
1,858
1,591
1,858
1.591
1,858
1.591
1,858
1,591
1,858
1,591 1.85«
1.591
1,858
1.591
1,858
1,591
1,858
.1.591
1,858
1.591
1,658
1.591
1,858
1,591
1,85«
1,591
1.858
BENEFITS
REVENUES TO
AUTHORITY FROM
MET VALUE OF TRAINING, CREDIT
TOTAL FARM PRODUCTION AND MACHINERY
14
156
800 40
/««
828
100
200
982 356 248
1.191 792 296
1.3» 1,284 344
1.423 1,786 392
1.530 2.2*8 440
1.634 2.820 488
1.737 3,353 536
1,831 3,895 584
1,927 4.449 632
1,723 5.012 680
1.803 5.587 728
1,889 6.172 776
2,003 6,769 824
2,095 7,378 872
2.189 7,997 920
2.278 8,629 968
2,368 9,272 1.016
2,457 9.928 1.064
2,547 10,595 1.112
2,638 11,275 1.160
2.730 11,967 1.208
2,819 12.672 1.256
2.909 13.391 1.304
3.000 14.121 1.352
3,091 14,866 I.4O0
3,180 15,623 1,448
3,270 16,395 1,496
3.359 17.182 1.544
3,449 17.980 1.592
3,449 18,795 1.440
3,449 19,142 1,440
3,449 19,398 1.440
3,449 19,593 1,440
3,449 19,788 1.440
3,449 19,986 1,440
3,449 20,187 1,440
3.449 20,388 1,440
3,449 20.592 1.440
3,449 20.799 1.440
3,449 21,006 1,440
3,449 21,216 1.440
3,449 21,429 1,440
3,049 21,642 1.440
3,449 21,858 1,440
3,449 22,077 1.440
TOTAL
40
100
200
604
1,088
1.628
2,178
2.738
3,308
3,889
4,479
5.081
5.692
6.315.
6,948
7,593
8,250
8,917
9.597
10,288
10,992
11,707
12.435
13.175
13,928
14,695
15.473
16,266
17,071
17,831
18,726
19,572
20,235
20,582
20,838
21,033
21,223
21.426
21,627
21,826
22,032
22,239
22,446
22.656
22,869
23,082
23,298
23,517
TOTAL 3,506 54.208 64,546 122,260 571.740 50,060 621,800

COL.
TABLE lfr-20
IRRIGATION DEVELOPMENT - ANNUAL COSTS AND BENEFITS
RATE 2-300,000 ACRES
£ x 1.000
Z. 3. ». 5.
COSTS BENEFITS
Y
MANAGEMENT AUTHORITY,
RESEARCH TRAINING
E
OPERATION AND
MAINTENANCE-
COTRE,
HEADQUARTERS A» SCHWE, REVENUES ID
A MAINTENANCE OF OAM, IRRIGATION/ AND OPERATION AUTHORITY FROM
R QUARRY AMD - DfUIMfiE SYSTEM, AND MAINTENANCE HCT VALUE OF TRAINING, CENTRE
TRUNR MAO
AMD ROADS OF MACHINERY TOTAL FARM PRODUCTION MO MACHINERY TOTAL
1
1»
1»
2 37 IS 156
3 37 22 2W 3X 40 40
4 37 62 93 402 100 WO
5
6
7
8
9
10
334
334
334
334
»34
334
1»
2Ï0
378
43J
SB«
590
•.
8TO
39
**
5»
m
TU
828
" '*©
Ù-W-
•,33*
h*87
1,633
356
792
1,26«
1.786
2,484
200
. 248
296
344 ..-.-;.
492 '
564
200
8Ä- ••
.-Mes
1,62«
i0à
3,048
II 334 651 SOI 1,786 1,232 636 3,868
12 334 717 878 1,929 4,021 708 4,73
13 18 788 962 1,758 4,825 780 5,605
14 887 1,050 1,937 ~ 5,644 952 6,596
15 993 1,1« 2,141 6,674 1,046 7,722
16 1,078 1.24« 2,324 7,764 1,144 8,908
17 1,161 1,344 2,505 6,901 1,240 10,141
i8 1,24« 1,442 2,686 10,060 1,336 11,396
19 1,325 1,5« 2,865 11,242 1,432 12,674
20 1,407 1,638 3,046 12,447 1,528 13,975
21 1,490 1,736 3,226 13,675 1,624 i5,299
22 1,591 1,858 3,449 14,925 1,820 16,745
23 1,591 1,858 3,449 16,411 !,440 17,851
24 1,591 1,858 3,449 • 16,901 1,440 18,341
25 1,91 1,856 3,449 17,214 1,440 18,654
26 1,591 1,858 3,449 17,385 1,440 18,876
27 1,591 1,858 3,449 17,559 1,440 18,999
28 1,591 1,85t 3,449 17,736 1,440 19,176
29 1,591 1,858 3,449 17,913 1,440 19,353
»
31
1,591
1,591
1,858
1,858
3,449
3,449
18,093
18,273
1,440
1,440
19,533
19,713
32 1,591 1,858 3,449 18,456 1,440 19,896
33 1.591 1,858 3,449 18,642 1,440 20,082
34 1,591 1,658 3,449 18,828 1,440 20,268
35 1,591 1,858 3,449 19,017 1,440 20,457
36 1,591 1,858 3,449 19,206 1,440 20,646
37 1,591 1,858 3,449 19,398 1,440 20,838
38 1,591 1,858 3,449 19,593 1,440 21,033
39 1,591 1,858 3,449 19,788 1,440 21,228
40 1,591 1,858 3,449 19,986 1,440 21,426
41 1,591 1,858 3,446 20,187 1,440 21,627
42 1,591 1,858 3,448 »;»? i,44û 21,828
43 I.SBi i.ôâè 3,449 20,592 1,440 22,032
%'-i i',a\ 1,858 3,449 20,799 1,440 22.239
45 1,591 1,858 3,449 21,006 1,440 22,446
46 1,591 1,858 3,446 21,216 1,440 22,656
47 1,591 1,858 3,449 21,429 1,440 22,869
48 1,591 1,858 3,449 21,642 1,440 23,082
49 1,591 1,858 3,449 21,858 1,440 23,298
SO ^___ 1,591 1,858 3,449 22,077 1,449 23,517
TOTAL 2,801 60,234 71,527 134,562 651,705 56.852 708,557
7.

-137- '
The various investment, annual cost and benefit streams connected with irrigation
development only have been presented in Tables 16-1A to 16-1D and 16-2A to 16-2D,
in which the two levels of development and the two rates of development, as previously
discussed, may be compared. The same information is shown in graphical form on Plates
20, 21 and 22.
The resulting internal rates of return for each of the four combinations of level
and rate of development are presented in Table 16-3 and also on Plate 23«
Level of development
Table 16-3 - Internal Rates of Return - Percent
250,000 acres 3,000,000 acres
Rate of development Rate 1 Rate 2 Rate 1 Rate 2
Irrigation development only
Irrigation development, plus
processing at 20 percent
return on book value
Irrigation development plus
processing at 30 percent
return on book value
9.6
11.2
12.0
IO.4
12.9
I3.9
9.7
11.5
12.6
Note: Period of analysis is 50 years and residual values are disregarded.
Irrigation development and processing
It can be argued that the rates of return calculated in the preceding section
might not present a fair measure of the profitability of the project. The benefits
are based on a certain level of farm income, which, in turn, is based on ex-farm prices
of agricultural produce or raw material. In some cases, the bases of valuing crops
are somewhat unusual. For example, sugar cane, which is valued as standing mature
cane, and kenaf, for which an ex-farm price as bundled green material was established.
Such values, however, facilitate evaluation of the farmer's income.
These ex-farm prices are such that processing is a profitable operation, as can
be deduced from the fact that such plants already exist elsewhere in Kenya, using
raw materials costing more or less the same. Since at least sugar cane has to be
processed shortly after cutting, an additional calculation of internal rates of return
has been carried out, taking into account the related benefits which oould be obtained
from processing.
As no refined calculations as to the exact type of plant and timing of construction
could be made, the results should be considered as indicative only. Two alternative
levels of benefits from processing are assumed, which bracket the range within which
any development in this respect would probably lie. In justification of this approximate
approach it may be noted that the assumed levels of return have been found to be
acceptable to similar private enterprises.
10.6
13.1
14.1

4
3
X
Z
<
1
ƒ i
f !
ƒ 1
'•
1 1
i f
! f
! f
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- — -
1
• 1
loiv :iopMtin •ATI t «
1 rs.
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7 f two X> ACIC» A
i
i
i
1
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7 f
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y\\
i
*x ^ A\ 1 1
r - "
j
OtVt[0PMKNT «ATI «> r - r " : 1
- " : 1
j
i
1
-4
NOTE: IMCLUDeS RllMVt»TMENT» FOI
AGRICULTURAL MACHINERY.
i
D.MO AC t»
1
_.. _.
1 '
>.
'. MO. OO ACtCI
l
\ \C-
l
; \
\
! \ ttO. IOO ACtCI 1 'v '\ \ \
\
\ L l K
^
\ 1 \ \ , -W ^._
1 \
VIA«
i
~
1
«OVCINMCNT IF KtllVA
UIÏITIO HATIONS »FECIAL FUNO
SURVEY OF IBII6ATI0N l'OTENTIAL
LOW» TA0A RIVER BASIN
FM» AH» MUCIATUH MUICATBW «f TUI UWTtOmlWB
IRBI6ATI0N DEVELOPMENT
STREAMS OF INVESTMENT
"UACO / ACRES
u^.
PLATE 20

3
s
z
4 I
,., ,
S\
•1 IIUIHII T 1WTI t
'vumiJMiin •» rt 4
_ . t—
—- T v »••.••< AMI»
\ v"»«i Acat*
! /
! i ! \
i /
Y I Af
NOTE: INllUOC» COM Or OMVATION OF AtlICUlTUCAl MACHINtBY.
OUT EXCLUDE» Alt OTHCf FAtM COSTS.
•
1
• ~
f
,
tOVCBHMtHT or KENYA
UNITED NATION» SMCIft rUNO
SURVEY OF IRRI6ATI0H. POTeHTIAL
LOW« TANA RIVES »A« h
m* âm AMKuiutt miantia w m i
IKKI6ATI0N DCVCLOPMCHT
ANNUAL COSTS

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CO»T» : TOTAL OF IMVtSTMENT ANO ANNUAL COSTS
EXPtNOITMC»: CO»T» • fAKMCK»' INCOME.
»fntrn» fitT VALUE or AÜIICULTUCAL PÏOOUCI
• etVtMUtS TO AUTHOtlTY.
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»•VIINMINT IF KINYA
(INITIO NATIONS »PtCIAl PUNO
SUBVIY OF
LOwte
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irtlCATION POTENTIAL
TANA tlVCC »ASin
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IKI6ATI0N DEVELOPMENT
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COSTS: TOTAL Or INVESTMENT AHO ANNUAL COSTS.
tIPCNOITUir.) : COSTS • FABMtlS' INCOMt.
erntrns N[T VALUE or AGIICULTUIAL PIODUCE
»UVENUtS 70 AUTHORITY.
NOTE:
FOI «00.000 ACItS AND DEVELOPMENT RATE l
fcOVEENHtNT OF KENYA
UNITIO NATIONS SPECIAL runO
SURVEY or ICBI6ATI0N POTENTIAL
LOWCS TANA KlVCt BASIN
FOOS ABB AHtcmtuU MAAWUTIOII Of Tut UIMTIS MIU
IRRIGATION DEVELOPMENT
ANNUAL BENEFITS AND EXPENDITURES
TO AUTHORITY
IL A CO / ACRES
p i A T e it
SNItT tHt

-142-
Thc t"o alternative levels or processing benefits are expressed in terms of a
return on average book value of capital investment in factory equipment and civil
works, including staff and skilled labour housing* of respectively 20 and 30 percent.
This return is assumed to be the difference between the gross ex-factory value of
processed produce and the combined value of agricultural raw material at the factory,
depreciation and costs for purchase of goods and services, such as fuel, spares, skilled
labour and management. It thus includes interest claims on the capital invested,
remuneration of unskilled labour and profits.
The investments which are required annually, and the corresponding book values,
were obtained by means of rather schematic and simplified calculations, as explained
hereinafter.
The amount of capital required to process the produce resulting from the selected
crop rotation plan into sugar, cotton lint, bags, oils and cakes was found to be in
the order of £ 200 per acre of fully productive land. Allowance was also made for
a compounded annual increase of one percent in plant capacity to cope with the similar
increase assumed for land productivity. The accumulation of the foregoing investments
provided the appropriate value of available capacity at any stage as development
expanded.
Factory and civil works were assumed to have an average economio life of 15 years,
hence a stream of reinvestments similar to the original investment stream was taken
into account with a time lag of 15 years. Total annual investment required for new
capacity and renewals were called gross investment.
The linear depreciation method was used, and the depreciation allowance for
each year thus amounted to 6-2/3 percent of the new value of available capacity at
the end of the previous year.
The difference between gross investment and depreciation allowance was called
net investment, and the accumulation of net investments resulted in the book value of
existing capacity.
To calculate the aggregate internal rate of return of irrigation development
and processing together, the two streams of benefits, as defined above, were summed,
whilst on the cost side the stream of net investments for processing was added to the
investment plus annual cost stream for irrigation.
Schematic streams of aggregate costs and benefits for two of the eight possible
combinations of levels and rates of development and returns from processing are shown
on Plate 24* For all eight combinations the internal rates of return have been
listed in Table 16-3 and are presented graphically on Plate 23.
16.2 Recovery of Costs from Beneficiaries
The charges to be levied on the farmers for the use of reclaimed land and the
availability of irrigation water would depend on a variety of factors. One of these
would be the farmers' capacity to repay which, in its turn, would depend on farm
income and tenant target income levels.

L E 6 E tl O
BI
B.2
Cl
C.2
P
P.20
P »O
NOTES:
DISCOUNT BATE - PER CENT
IRRIGATION BENEFITS. DEVELOPMENT RATE t.
IRRIGATION BENEFITS. DEVELOPMENT RATE Î.
TOTAL OF INVESTMENT AND ANNUAL COST» OF IRRIGATION
DEVELOPMENT. RATE «.
TOTAL OF INVESTMENT AND ANNUAL COSTS OF IRRIGATION
DEVELOPMENT. RATE 2.
MET INVESTMENT IN PROCESSING FACILITIES.
PROCESSING BENEFITS: 20 PER CENT OF BOOK VALUE OF INVESTMENTS.
PROCESSING BENEFITS: 50 PER CENT OF BOOK VALUE OF INVESTMENTS.
PERIOD OF ANALYSIS 50 VEARS.
RESIDUAL VALUES AT END OF PERIOD DISREGARDED.
GOVERNMENT OF KENYA
UNITE» NATIONS SPECIAL FUND
SURVtY OF* IRRI6ATI0N POTENTIAL
LOWER TANA RIVER BASIN
rtop Aito «ticuuim ottAniuTion OF THI unmo IUTIOIK
INTERNAL KATES OF RETURN
250.000 ACRES
IL A CO / ACRES
PLATE 23
»MltT * 0' 1

o »e
LEGEND
8 4
Cl
C.ï
P
P.IO
P»o
NOTES:
« « n
DISCOUNT BATE - PEK CENT
IBBI6ATION »ENEFITS. DEVELOPMENT tATE I.
IEBI6ATI0N BENEFITS, DEVELOPMENT IATE »
TOTAL Of INVESTMENT AND ANNUAL COST» IP IttlûATIOH
DEVELOPMENT.BATE

-145-
On the other hand, the type of development envisaged is of such magnitude that it
would"' not only involve a large number of other nori-agricultural people in the area
but also provide considerable benefits to the country. This makes it unreasonable
to expect the farmers to cover all of the annual costs of operating the project, and ..
also to repay the capital cost. Such a course would be especially unfair to the ijjeéi
generation of farmers. It would be reasonable to recognize that during the ini^rfal
years many unexpected frustrations and disappointments would be encountered, which
should not be aggravated by a high level of levies, rigidly imposed to meet a fixed
repayment schedule.
Further, the proposed Tana River Irrigation Authority would presumably be
responsible for research, for the training of staff and tenants and for the provision
of extension services also. The cost of these tasks is included in the economic
analysis. Since farmers in traditional farming areas usually do not pay directly
the costs for demonstration farms and extension services, a similar approach might be
advocated for the Tana development.
In view of these considerations, it is proposed a reverse point of view be adopted
and tenant income be given priority over scheme debts, so that the pioneer farmers
especially are induoed to contribute willingly the rigorous and sustained effort
demanded by irrigated cultivation. Assuming that the scheme Authority will be a semigovernmental
institution, backed financially by the Government, the financing of scheme
debts can be achieved in various ways. In Seotion I6.4» one particular method of
finanoing is discussed in some detail»
PossiDie arrangements as to how charges on cultivators should be individually
assessed and collected include:
(a) on measurements of the actual amounts of water used;
(b) at uniform rates per acre of holdings;
(c) at uniform rates per acre of each of the various crops grown;
(d) at a percentage of the actual or assessed value of the crops
actually grown each year by each cultivator.
Each of these has merits and disadvantages, (a) Tends to economise in the use
of water, but is not easy to apply in practice, especially with inexperienced cultivators,
(b) Is very rigid, and puts all the risk of variations in yields (e.g. in bad
years) on the individual cultivator, (c) Is similar, though slightly less so; it
involves elaborate records, (d) Is fair to the cultivator, and flexible, but in
application it involves centralised marketing of the crops to which it is applied;
it is the method used in the Sudan Gezira Scheme, being applied there to the cotton
crop.
Fo specific recommendations are made for a particular method. But the need
to consider the point very thoroughly is stressed, so as to reach sound conclusions
about it before development begins. Its implications are practical, social and
economic.
I6.3 Tenant Income
In the studies made, the target level of tenant income was set at £ 160 per family.
It was assumed that this level would apply to the very first farmers who start in the

-146-
scheme area proper after a year of training i» +>>e P.esesreh ind Tz aluin« Centre..
Thermal lex-, it was assumed that the same annual increase in real income of 2 percent
as adopted for scheme authority personnel, would also apply to the tenants.
"*>^hi8 could not continue indefinitely, because the productivity of the land was
assumed to increase only at one percent per annum. Thus, in the course of time,
the land use pattern would have to be changed toward maximizing output per farmer
rather than per acre as assumed in the initial labour-intensive stage of development.
How this change would be realized was not further discussed in the studies. For the
eoonomio analysis, it was assumed that it would take place once tenant incomes reached
a level of £ 250 per original five-acre holding. From then onwards, farmers' income
would remain at £ 50 per acre. As it was assumed that lower yields would be obtained
by farmers during the first two years of cultivation on new land, the same reduction
was applied to income as well.
As discussed in Chapter XTV, nousing is a consumer good for which, in principle,
users should pay the costs. The initial target level of income, however, is suoh
that it would be almost impossible for a tenant to pay the full cost of the proposed
type of housing. The relevant cost is estimated to be in the order of £ 40 P©r annum
or 25 percent of the basic income level. In the finanoial analysis discussed in
Section 16.4, a gradually decreasing rent subsidy to tenants by the scheme authority
was taken into account.
16.4 Financial Analysis
The internal rate of return analyses made in the studies provided a macro-economic
assessment of the situation. The financial analysis was based upon the concept that
the authority had to take care of itself in the procurement of funds and in servicing
them with project revenues remaining after all other payments had been made. The
previous analyses of internal rates of return did not take into account the remuneration
of what might be called labour with zero return opportunity. In practice,
however, the scheme authority would have to leave the farmers a sufficient part of the
farm output as income, and processing industries would have to pay wages to the unskilled
labour as well. This means that, in fact, the authority would require additional
funds for quite a considerable period to finance the development programme
(see Plates 22 and 24).
Hereunder, an attempt is made to set out whit are the implications of a particular
form of financing. The basio assumptions and considerations have been as follows:
(a) Two form8 of funds have been distinguished, domestic and foreign
loans. The types and terms of foreign loans available are
restricted aüd less flexible than those which may be possible with
funds obtained domestically. Therefore, by adopting certain
alternative terms for the domestio component, the analysis leads
to various conclusions as regards the possibilities which remain
open for the foreign component.
Following the same procedure as in previous calculations, investments
and annual costs for infrastructure and tenant housing
have not been included. In Section 16.3, a gradually decreasing
rent subsidy to tenants has been suggested. This subsidy has

•••
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I t GC NO NOTt:
CO»T» : TOTAL Of INVt»THCNT ANO. ANNUAL C04λ FOI IttlGATION
«NO HIT INVIÏTMtHT IN PIOUMIN6 fACILITHS
tlPtNDITUtt»: CMTS • fACHt»' INCOMf AND WAGt» Or UNftKILLtD
LAtOUl IN PBOCtSilN«.
fctMtriTS NET VALUt Of A6IICULTUIAL PKOOUCt • ttVtNUt» TO
AUTNOtlTV • JO PCt CtNT ttTURN ON MOK VALUt Or
invt»TMtNT m Pioctssmo rACiiiTieo.
VI AI
... -
rot 1(0.000 ACBf.4 ANO DtVlLOPMtNT RATC 1.
•latriT»
C»T»
= *~~
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—"""
OtVltNMtNT
UNITt* NATIONS
Or KtNVA
»PtClAl »UN»
SUBVtV Or I»BI6ATI0M POTENTIAL
10W(S TANA BIVtC «ASIN
row An» AMICWTMC uttmxnm or m uaim «mom
TOTAL ANNUAL
BENErTTi AND'EXPENDITURES
OF IRRIGATION AND PROCESSING
!£_•_•__„. PLATE 24
IL A 1 [_ oyActt» n
•MIT ( m %
I
•

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s."
S:
1 =
.
•
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L E CENP
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s
/
s
/
/ ^ S~
/
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COSTS: TOTAL OF INVESTMENT ANP ANNUAL COSTS FOR IRRIGATION
ANP NET INVESTMENT IN PROCESSING FACILITIES.
EIPENPITURES: COSTS • FARMERS' INCOME ANP WAGES OF UHSKIllEO
LABOUR IN PROCESSING.
BENEFITS: NET VALUE (IF AGRICULTURAL PROPUCE • REVENUES TO
AUTHORITY > SO PER CENT RETURN ON BOOK VALUE OF
INVESTMENT IN PROCESSING FACILITIES.
f -"*
.-/'
\
>
^
\.-, .
NOTE:
YEAR
-^"
— -
.—- T'
i
^•"""~
FOR SOO.OOO ACRES AND
PEVELOPMENT .RATE 1.
il
!
i
|
!
I
i
•intrus
S ^
ttw/
,
" ^
~ 0 =
ttVERNMENT OF KENYA
UN1TCP NATIONS SPECIAL »UfO
SURVEY OF
LOWER
IRRI6ATI0N POTEIITIAL
TAMA RIVER »ASM
f000 AHO AttlCUlTUtt OttAIMATION OF THE UTII1 (S IUTBIIS
TOTAL ANNUAL
BENtflTS AND EXPCNDITUIteS
OF IRRIGATION AND PROCESSING
ILACO / ACRES
PLATE
SHItT II
24

-149-
been assumed to be £ 20 per tenancy in the base year and to decrease
by £ 1 per year, which amount is lower than the assumed two percent
increase in real income. The real expenditures at tenant level for
the scheme Authority start thus at £ l80 per five acres or £ 36
per acre. ¥hen the subsidy ends after 20 years, per-acre income
would have reached a level of £ 47.60. Three years later it will
have reached £ 50» at which level it is assumed to remain constant.
The cost of wages for unskilled labour has been assumed tofbe one-third -of
the return obtained in processing, as defined in Section 16.1. ^
(c) Within the 50-year period of over-all analysis, two sub-periods have
been distinguished. During the first period, I, total expenditures
still exceed benefits, whilst during the second period, II, benefits
exceed scheme expenditures for investments, operation, maintenance
and payments to tenants and labour (see Plates 22 and 24).
(d) During period I, 50 percent of the deficits will be financed by
domestic loans from the central Government, on which interest
charges will not be paid, but accumulated to the outstanding,
growing debt. Two alternative rates of interest have been used,
as indicated in Table 16-4.
(e) The accumulated domestic debt at the end of period I will not be
amortized, but perpetuated as a permanent loan. This procedure is
acceptable as long as the perpetuated debt stands in good proportion
to the residual value of the project at the end of the period of
analysis.
(f) During period II» the excess benefits will be used in the first
instance to pay interest on the permanent domestic loan. As it is
possible that the benefits would not be sufficient to cover this
charge during the initial years of period II, a temporary additional
deficit could occur.
(g) As a result of the previous calculations, it appears that there
would be a balance of deficits during period I and possibly during
the first part of period II, and thereafter a balance of excess
benefits.
It has been assumed that the stream of defioits woul be matched by foreign loans,
which could be fully amortized out of the excess benefits by the end of the period of
analysis. The internal rate of return corresponding to this "foreign finance" stream
indicates the average rate of interest and the average maturity period at which
foreign loans could be contracted. It does not, however, provide an answer as to how,
in reality, certain types of foreign loans should be finanoed and refinanced. Insofar
as, in practice, debt servioe on foreign loans - that is payment of interest or amortization
- will be required during the period of continuous defioits, the assumptions
used herein imply that these payments would be refinanced by additional loans.
Analyses have been made based upon.the foregoing for the two extreme alternative
developments; that is, development of irrigation on 250,000 acres at the slow rate
of development, and on 300,000 acres at the fast rate. In addition, the alternatives
with processing included have been considered. The results of these various calculations
have been summarized in Table 16-4«

Level of development
Rate of development
Return on investment in processing
Length of sub-periods=/
Rate of interest on dom«stic debt
Accumulated domestio debt, including
interest, at end of period I and
during period II
Residual value of assets at end of
period IlS/
Annual interest charge on permanent
domestic debt during period II
Rate of return on foreign finanoe
Foreign debt still outstanding at
end of period II
l/ Period of analysis 50 years.
Table 16-4 - Specimen Representative Financial Analysis
Irrigation Development
Unit
acres 250,000
1
years
million
£
million
£
million
£
million
£
28/22
0 3
35 58
60
0 1.7
1.0 0
27
Irrigation
development
300,000
2
23/27
0 3
39 53
70
0 1.6
1.5 0
21
Irrigation
development pitta
processing
250,000
1
20
23/27
3 6
45 71
100
1.3 4.3
4.5 1.0
2/ Residual value obtained by assuming that Korokora dam and the irrigation, drainage and internal
roads systems are well-maintained and still have a value close to their original construction
cost. On-farm and processing investments have been taken at their book value.
300,000
30
18/32
3 6
41 54
120
1.2 3.3
8.0 5.5

-151-
Frora the preceding analyses, the following conclusions can be formulated:
(a) When irrigation development alone becomes the responsibility of
the scheme Authority, foreign financing is only possible at soft
terms, provided the domestic funds are available to the Authority
free of interest« Even low interest charges on domestic capital
would exclude any payment of interest on foreign loans.
(b) The situation becomes more favourable when processing is included.
In that case, more realistic types of foreign financing are possible.
A prerequisite is, however, that the scheme Authority has full control
over the processing activities, so that the profits therefrom are
directly available for debt service.
I6.5 Estimate of Total Required Investment
Tables I6-5A to 16-5D present summaries of the order of total investment required
for project development» including the related investments for trunk road, infrastructure,
tenant housing and processing facilities.
16.6 Foreign Currency Aspect of Project Development
Expenditures in foreign currency are required for initial capital investments
and reinvestments, maintenance of the various works and purchase of inputs for agricultural
production and processing.
Gross revenue consists of the sales value of agricultural production» of which part
would be exported and the balance would save foreign currency by import-substitution.
For the irrigation or agricultural part of development, a summary of the situation
with respect to costs and benefits is presented in Tables 16-6A to 16-6D. Therein,
gross proceeds from the sale of agricultural produce have been calculated at the
processed level, that is, in the form of sugar, cotton lint, and groundnut and cotton
seed, oil and cakes. As import values for some products, such as sugar, may be somewhat
lower than the ex-factory values, the foreign exchange value of agricultural
produce has been taken at £ 125 Per acre in the base year (year 6 of the cash flow
stream). The expenditure consists of 50 percent of the capital investments for the
irrigation system, excluding the dislocation allowance and credit to farmers, and the
annual running cost, which has been estimated at 15 percent initially. This latter
cost is assumed to decrease gradually to 10 percent per annum. The foreign currency
component of capital expenditure for processing has been taken at a similar level of
50 percent of gross investments.
The annual expenditures in agricultural production and processing for the purchase
of goods and services such as spare parts for agricultural machinery, fertilizers,
chemicals, fuels and, initially, expatriate managerial skill, have been estimated only
approximately and taken as £ 20 per acre throughout the whole period of analysis.

COL.
- 152 -
TABLE I6-5A
TOTAL REQUIRED INVESTMENT
RATE I - 250.000 ACRES
. £ x I.000
2. 3. 4.
Y INFRASTRUCTURE
E
A
R
IRRIGATION
' TOWNSITES
AND PROCESSING
DEVELOPMENT TRUNK ROAD HOUSING FACILITIES TOTAL
I I.I50 1,700 800 3,650
2 2,350 3,400 1,200 6.950
3 3,700 3,400 2,000 9,100
4 4,500 4,000 8,500
5 6,150 4,000 1,500 11,650
6 5,100 4,000 1,750 10,850
7 2,200 4,000 1,850 8,050
8 2,150 4,000 1,750 7,900
9 2,300 4,000 1,650 7,950
I0 2,250 4,000 1,550 7,800
II - I5 10,500 20,000 6,150 36,650
I6 - 20 11,200 20,000 4,800 36,000
2I- 25 10,300 20,000 10,500 40,800
26 - 30 7,200 8,000 6,200 21,400
3I - 35 1,000 500 1,500
36 - 40 1,000 550 1,550
m - 45 1,000 600 1,600
46 - 5Û I.OUO 650 1,650
TOTAL 75,050 8.500 100,000 40,000 223,550

COL. I.
Y
E
'A
R
1
IRRIGATION
DEVELOPMENT
1,150
- -.; 153 -
TABLE I6-5B
TOTAL REQUIRED INVESTMENT
RATE 2 - 250,000 ACRES
£ x I,000
2. 3. 5.
TRUNK ROAD
INFRASTRUCTURE
TOWNSI TES
AND
HOUSING
1,700 800
PROCESSING
FACILITIES
TOTAL
3,650
2 2,350 3,100 1,200 6,950
3 3.700 3,100 2.000 9.100
1 1,500 1,000 8,500
5 6,150' 1.000 1.500 11,650
6 5,150 1.000 1,750 10,900
7 2,100 6,000 1,850 10,250
3 3,100 .
" • - • - • 6,000
1,750 11.150
9 3,000 6,000 2,100 11,100
10 3,200 6.000 2.150 11.650
II - 15 19.200 38.000 12,250 ' '69.450
16 T 20 15.700 22.000 11.100 18,800
21-25 1,600 1,700 3,300
26-30 1.000 1.750 2,750
31 - 35 I.OOÖ 1.800 2.800
36 - HO 1.000 • 1.850 2.850
HI - 45 1.000 • 1.900 2.900
46 - 50 1.000 . 1 .950 2,950
TOTAL 76,500 8:500 100,000 16.000 231.000

- 154 -
TABLE I6-5C
TOTAL REQUIRED INVESTMENT
RATE I - 300,000 ACRES
£ x 1,000
COL. I. 2. 3. t. 5.
Y
E
A
R
IRRIGATION
1 1,150
DEVELOPMENT TRUNK ROAD
INFRASTRUCTURE
TOWNS 1 TES
AND
HOUSING
1,700 800
PROCESSING
FACILITIES
TOTAL
2 2.350 3,400 1,200 6,950
3 3,700 3,400 2.000 9,100
4 4.500 4,000 8,500
5 6,150 4,000 1,500 11.650
6 5,100 4,000 1.750 10,850
7 2.200 4,000 1.850 8,050
8 2.150 4,000 1.750 7.900
9 2,300 4,000 1,650 7,950
10 2.250 4,000 1,550 7.800
Il - 15 10,500 20,000 6,150 36.650
16 - 20 11,200
"
3,650
20,000 4,800 36,000
21 - 25 10,300 20,000 10.500 40,800
26 - 30 10,400 20.000 8,300 38,700
31 - 35 7,400 8,000 2,900 18,300
36 - 40. 1,200 3,000* 4.200
41 - 45 1,200 3.100 4,300
"»6 - 50 l,2fK) 3,200 4.400
TOTAL 85,250 8,500 120,000 52/000 . 265,750

- 155 -
TABLE I6-5D
TOTAL REQUIRED INVESTMENT
RATE 2 - 300,000 ACRES
£ x I,000
COL. I. 2. 3. *.
Y
E
A
R
I
IRRIGATION
DEVELOPMENT
1.150
TRUNK ROAD
INFRASTRUCTURE
TOWNSITES
AND
HOUSING
1.700 800
PROCESSING
FACILITIES
TOTAL
2 2,350 3.400 1.200 6.950
3 3,700 3.400 2,000 9.100
4 4,500 4.000 8.500
5 6,150 4.000 1.500 11,650
6 5.150 4,000 1.750 10,900
7 2,400 6,000 1.850 10,250
8 3,400 6,000 1.750 11,150
9 3,000 6,000 2,400 11,400
I0 3,200 6,000 2.450 11,650
Il - IS 19,200 38,000 12.250 69,450
I6 - 20 19,900 42,000 12.300 74.200
21 - 25 7,100 6,750 13,850
26 - 30 1.200 1.200 2,400
31 - 35 1.200 1,300 2,500
36 - 40 1,200 1.400 2.600
41 - 45 1,200 1,500 2,700
46 - 50 1,200 1,600 2,800
TOTAL 87,200 3.500 120.000 50,000 265,700
3.650

COL.
Y
E
A
R
- 156 -
TABLE I6-6A
FOREIGN CURRENCY ASPECTS.OF IRRIGATION DEVELOPMENT
GROSS
PROCEEDS
RATE I - 250,000 ACRES
£ x I ,000
I. 2. 3. 4.
IRRIGATION SYSTEM
INVESTMENTS
AND
ANNUAL COST
I 600
EXPENDITURES
FARMING AND
PROCESSING
INVESTMENTS AND
ANNUAL COST
TOTAL
(2 + 3)
BAUNCE
(1 -4)
600 - 600
2 1,200 1,200 - 1,200
3 1,900 1,900 - 1,900
4 2.300 2,300 - 2,300
5 3,050 750 3,800 - 3,800
6 950 2,400 1,100 3,500 - 2.550
7 2,100 1.100 1,450 2,550 - 450
8 3,400 1,100 1,650 2,750 + 650
9 4,700 1,200 1,900 3,100 + 1,600
I0 6.050 1,200 2.100 3,300 + 2,750
II - I5 51,400 5.500 13,800 19,300 32,100
I6 - 20 89.200 6,000 20,200 26,200 . 63,000
2I - 25 130,700 5,800 30,200 36.000 94,700
26-30 176,300 4.500 35.600 40,100 136.200
3I - 35 204,100 2.000 33,900 35,900 168,200
36-40 214,700 2,000 39,000 41,000 173,700
HI - 45 225,700 2,000 39.400 41,400 184.300
46 - 50 237.200 2,000 35,800 37,800 199,400

- 157 -••
TABLE I6-6B
FOREIGN CURRENCY ASPECTS OF IRRIGATION DEVELOPMENT
RATE 2 - 250,000 ACRES
£ x I,000
COL. I. 2. 3. ¥. 5.
Y
E
A
; R
GROSS
PROCEEDS
IRRIGATION SYSTEM
INVESTMENTS
AND
ANNUAL COST
i 600
2 1,200
3 1,900
1 2,300
EXPENDITURES
FARMING AND
PROCESSING
INVESTMENTS AND
ANNUAL COST
5 3,050 750 r
6 950 2,100 1,100 '
7 2,100 1,200 1,150
8 3,100 1,750 1,650
» 1,700 1,600 2,250
10 6,550 1,600 2,700
Il - 15 61,200 9,800 19,600
16 - 20 132,600 8,000 32,100
21 - 25 183,600 2,100 33,300
26- 30 191,100 2,000 36,100
3II - 35 201,300 2,000 39,200
36-10 211,700 2,000 35,100
Il - 15 225,700 2,000 37,900 •
16 - 50 237,200 2,000 11,100
TOTAL BAUNCE
(2 + 3) (I -1)
600 - 600
1,200 - 1,200
1,900 - 1,900
2,300 - 2,300
3,800 - 3,800
3,500 - 2,550
2,650 - 550
3,100 0
3,850 + 850
1,300 2,250
29,100 34,800
10,100 92,500
35,700 117,900-
38,100 156,300
11,200 163,100
37,100
177,600
39,900 185,800
13,100 191,100

COL.
Y
E
A
R
1
- 158 -
TABLE I6-6C
FOREIGN CURRENCY ASPECTS OF IRRIGATION DEVELOPMENT
GROSS
PROCEEDS
RATE I - 300.000 ACRES
£ x 1,000
2. 3.
I. "*.
IRRIGATION SYSTEM
INVESTMENTS
AND
ANNUAL COST
600
EXPENDITURES
FARMING AND
PROCESSING
INVESTMENTS AND
ANNUAL COST
TOTAL
(2 + 3)
5.
BALANCE
(1 -M)
600 - 600
2 1.200 1,200 - 1,200
3 1,900 1,900 - 1,900
M 2.300 2.300 - 2,300
5 3,050 750 3,800 - 3,800
6 950 2. MOO 1,100 3,500 - 2,550
7 2,100 1,100 I.M50 2,550 - M50
8 3, MOO 1,100 1.650 2.750 + 650
9 M.700 1.200 1,900 3.100 + 1,600
10 6,050 1.200 2,100 3.300 + 2,750
II - 15 51,MOO 5,500 13,800 19,300 32,100
16 - 20 89.200 6,000 20,200 26,200 63,000
21 - 25 130,700 5,800 30,200 36,000 9M.700
26 - 30 176,300 6.000 36,500 M2.500 133,800
31 - 35 226.100 5.000 M2.600 M7.600 178,500
36 - MO 257,500 3.000 MM.MOO M7.M00 210,100
Ml - M5 270.800 2.600 M5.700 M8.300 222,500
16 - 50 28M.600 2,300 M6.800 M9.I00 235,500

- 159 -
TABLE I6-6D
FOREIGN CURRENCY ASPECTS OF IRRIGATION DEVELOPMENT
RATE 2 - 300,000 ACRES
£ x 1,000
COL. I. 2. 3. *. 5.
EXPENDITURES
V IRRIGATION SYSTEM FARMING AND
E INVESTMENTS PROCESSING
A GROSS AND INVESTMENTS AND TOTAL BALANCE
R PROCEEDS ANNUAL COST ANNUAL COST (2 + 3) (1-4)
1 600 600 - 600
2 1,200 1,200 - 1,200
3 1,900 1,900

16.7 Conclusions
-160- \.
The methods adopted for the economic evaluations and financial analyses made in
the original project studies, the results of which are set out above, were, well suited
to the purposes envisaged. These results will, however, have to be re-estimated and
re-presented. In one respect, it is true, no major change in the basis of evaluation
need yet be assumed; while the cropping pattern used in the studies is queried (see
paragraph 9»6), other cropping patterns can be envisaged which can provide similar
rates of net farm revenue per acre. To this extent, the eoonomio evaluations set out
above remain valid. The need to consider other various points must be stressed, in
particular the economie implications of providing incentives, financial and other, to
attract cultivators, and to ensure adequate efficiency of production as well as
social satisfaction.
The eoonomio evaluation made indicate internal rates of return ranging 'from 9,6
percent to 14.1 percent on the cost of the ultimate development, on various assumptions,
as set out in Table 16-3. However, no economio appraisal can be regarded as
fully adequate, which does not take into its scope all the various items of expenditure
which are involved, directly or indirectly, in the development contemplated,
so as to present a comprehensive pioture of the whole. In the case of the Lower
Tana Scheme, aooount has to be taken of the costs of all items of the infrastructure
and ancillary costs, as well as those items which are directly concerned with the
development of irrigation. For convenience, the main figure are summarized as
followst
Assumed irrigable area - 250,000 acres
E.A. £ million £,/acre
Irrigation development 53.0 212
Processing plants 40.0 160
Housing, townsites and services 100.0 400
External trunk road (to Mombasa) 8.5 34
201.5 806
It is true that about half of this formidable total represents provision which
might conceivably be necessary, if not on the lower Tana, then somewhere else in Kenya.
However, expenditure on this scale, even though spaced over many years, cannot be
contemplated without the most thorough and critical scrutiny. This scrutiny must
include realistic appraisal under four main aspects, viz :
(a) the standards of provision assumed, e.g. for housing, for roads, and
for public services, such as water supply, sewerage systems, and so on;
(b) the designs and types of material assumed, and the unit rates of
cost involved in the execution of the works;
(c) the production and benefits to be expected;
(d) consideration of the resulting scheme and all its various implications,
with the revised forecasts of its benefits, not merely on its own
merits, but also in the broader field of the advantage to Kenya of
undertaking such a scheme, and the degree of priority that it deserves
in comparison with other potential investments in the country.

-161-
Erom the financial analysis discussed in paragraph 16*4» the results of which
are set out in Table 16-^4, the studies reached the following conclusions:
(i) If the Irrigation Authority is responsible for the development of
irrigation only, foreign financing is possible only on "soft" terms,
and on the assumption that domestic funds are available free of
interest.
(ii) If the Authority is also responsible for processing, more realistic
foreign financing becomes possible, provided that the Authority has
full control of that processing.
It will be noted that the financial analysis does not take within its scope the
provision of infrastructure and the external trunk road to Mombasa. On the basis
assumed, the analysis is clear and well presented, and there is no reason to disagree
with the resulting conclusions (i) and (ii) above. It remains to be seen what
conclusions «nay result from a revised appraisal and economic evaluation, following
the re-consideration recommended in this report, in line with points (a) to (d) set
out above.

17«1 Requirements
-162-
FURTHER STUDIES ABD INVESTIGATIONS
CHAPTER XVII
The development of the water resources potential of the Tana river represents
an undertaking so vast in terms of commitment of financial resouroes and manpower
as to warrant the most careful consideration of all aspeots in muoh greater detail
than has been appropriate under the terms of the studies made for the project. It
is believed^ as discussed in earlier chapters of this report, that an economically
viable power development of the middle Tana is possible. It must be recognized
however, that economic evaluation of the irrigation potential has been based upon
the results of only two years of agricultural experiments and trials« Hence,
although, as discussed in Chapter XVI, a marginally economic development.of irrigated'
agriculture may be postulated, there are a great many matters which require further
investigation, particularly in respeot of irrigated cultivation, before undertaking
suoh a major development«
The small irrigation projeot whioh was started at Qalole some ten years ago
has since been operated by the Kenya Government essentially as a settlement scheme.
At a later stage, it was set up as a pilot projeot for the development of a major
scheme, but has yet to serve this purpose« At the present time, it requires a
major overhaul of physical facilities, and of its organization and administration,
if it is to function effectively.
As a result of the preliminary indications,apparent in the course of the
projeot studies,that technically a large-scale irrigation scheme appeared to be
feasible, the Government of Kenya has put in hand arrangements to rehabilitate the
existing Galois scheme to serve as a small pilot demonstration unit« It is hoped
that it will be possible to complete the refurbishment of the existing scheme before
the end of 1968. Once oompleted, Galole may continue to serve as a pilot demonstration
scheme, in which investigation of some of the many problems that remain to be
solved can be undertaken. If a major irrigation development is to be undertaken,
it is 'imperative that the agronomic investigations be oontinued and extended, both
in time and space, to provide a sound basis for further assessment of its feasibility.

-163-
Further agronomio studies are also necessary to extend the experimental
results carried out under olose oontrol of research personnel to conditions of
tenant farming. A study should be made of the systems of mechanization best suited
to the requirements of smallholdings and to cropping patterns envisaged« Labourintensive
and mechanized cultivation practices should.be studied in further detail.
. Geomorphologie^ hydrologio and pedologio studies are recommended to evaluate
further such matters as the possibility of creating, by irrigation, a perched water
table, or of raising the generally deep groundwater level. Such information is
necessary to ensure that the unfortunate experiences of water-logging and salinization
whioh have occurred in other irrigation schemes can be avoided.
As indicated in the report, it has been necessary to plan for the cultivation
of soils which must, in fact, be considered marginally suitable, even though
satisfactory crop yields have been obtained on such soils under experimental trial
conditions. These soils are generally saline and/or saline-alkaline at depth, and
there is an urgent need to ascertain the feasibility or otherwise of reclamation
measures to improve and maintain the fertility of subsoils over long periods of
time, particularly in respect of soils of Class 3 suitability.
Whilst a technically sound irrigation scheme may be designed, its success or
failure is ultimately dependent upon the peoples who must grow the orops and process
them for market. Studies should be made of the methods and eriteria for selection
of prospective tenants, their training, and of the rules and regulations under
which the rigorous discipline necessary for irrigated cultivation may be successfully
imposed.
Sinoe, as has been mentioned throughout this report, the irrigation scheme
postulated herein is dependent upon developing a major series of dams and reservoirs
to control and regulate the flows of the river, for hydro-electric power it is essential
that the planning and development studies for this power system be carried
further. The additional investigations considered essential at this time are the
proving of site foundation conditions at those sites recommended for development
and, in oonsequence, the review and reconsideration of layouts and cost studies as
presented herein. As a part of the general evaluation of the power system proposed
for the Tana river, it is recommended that a system power study be made which will
enable economies to be realized at various projects through recognizing more fully
the function and capability to be achieved at each projeot. A re-appraisal of the
load growth forecast will be necessary at the same time. It may well be desirable
to inolude in these studies the effeot of interconnection of the coast with the
Nairobi and western Kenya system and also, as has been indioated recently, the possibility
of further interconnection between the Kenya and Uganda power grids.
The sociological implications of development have been referred to in this
report. It is emphasized that the brevity of these discussions should not, by any
means, be taken to be indicative of the relative importance attached to such
factors. In faot, it is strongly recommended that the sociological aspeots of
settlement of the proposed irrigation scheme in the lower Tana be investigated
without delay, and also that, at the same time, the related matter of the displacement
and rehabilitation of the riverine Pokomo population be given due consideration.

-164-
In order to as«««« *W« ?ooiolosicil, ëocrrc=ic. and financial i'üplioa'tluxiH
of development, both at the scheme level and to the nation as a whole, detailed
surveys and investigations must be carried out on communications networks, urban
development, governmental services, project organization and administration,
secondary production activities, processing facilities, warehousing and marketing
of produce.
Further, and in particular, the proposed 8,300-acre pilot scheme should be
primarily a productive unit rather than merely a centre for research and training.
The technical design and layout of this should be undertaken as soon as its social,
practical, and economic implications can be satisfactorily assessed, and its advantafes
and disadvantages realised. It should be appraised, both as a scheme in itself
even if it only so continues as such for a limited period of years), and as an instalment
of the full development, in both oases not only in its own merits, but also in
comparison with other potential developments in Kenya, and thus receive its appropriate
degree of priority in the national programme of development.
17»2 Ways and Means
Many, perhaps most, of the recommendations made in this report for the further
collection of data, and of the use of such data in analysis and comparative studies,
will involve work which can best be done by Government departments and agenoies
in Kenya. It will primarily be for the Government to decide how far this course
will be possible, and then in what manner and to what extent they may wish to seek
for external help in carrying put the remainder of the work involved.
It appears desirable, however, to emphasize the importance of early action
to resolve the various problems and carry out the various studies, so that planning
for and decisions about this very large and important projeot can proceed without
undue delay, and on sound foundations.

-165-
PLAN OP OPERATION
UNITED NATIONS SPECIAL POND.
KENYA - SURVEY OF THE IRRIGATION POTENTIAL
OF THE LOWER TANA RIVER BASIN
SUMMARY
ATPMPIX I
Special Fund Allocation* S 974,100
Including: a) Special Fund Contribution
(including Agency overhead
costs)
$888,500
b) Government payment towards
local operating costs
Government Counterpart Contribution in Kind
? 85,600
Equivalent of» $ 619,800
Duration t 3 years
Cooperating Government Agency« Ministry of Land Settlement
and Vater Development
For the purpose of the survey of the Tana River basin for development of the
irrigation potential to be undertaken by FAÖ acting.as the Executing Agenoy for
the UN Speoial Fund, this Plan of Operation shall be the Plan of Operation provided
for in Article I, Paragraph 2 of Agreement signed on 7th January I96I by.the
Government of the United Kingdom, on behalf of the Government of Kenya, and the
UN Special Fund.
* Agenoy overhead oosts and Government payment towards local operating costs
are inoluded in the Speoial Fund Allocation.

A. Purpose
-166-
1. PURPOSE AND DESCRIPTION OF THB PROJECT
1. The purpose of the Project is to provide for Government an assessment of the
potential development of irrigated agriculture in the Lower Basin of the Tana River,
which may facilitate the settlement there of surplus peasant people from densely
inhabited areas elsewhere in Kenya. In the Lower Basin, extensive plains of empty
lands, lying close to a good source of water for irrigation, offer natural prospeots
for agricultural development at moderate cost. In the middle reaches of the river
are the main potentialities of developing hydro-electric power. In the Upper Basin,
the more rolling country offers better prospects of sites for storage reservoirs
than the flat plains of the Lower Basin; some irrigation possibilities also exist
there, which have in part been already developed. Although the present project
relates only to development in the Lower Basin, it is clearly necessary in. the
investigations to consider the whole basin of the river as one hydrological unit.
The headquarters of the project will be in Nairobi.
B. Description
2. The period of the Project will be 3 years. The work to be done consists of the
following items:
(i) Preliminary reconnaissance survey over an area estimated
to be about 3 million acres, with the object of selecting
areas, expected to be a total of about 0.6 million acres,
for more detailed examination.
(il) Carrying out Ground Control, and basic levelling, and
mapping of 600,000 acres of selected areas on suitable
scales for soil surveys and other purposes of the project.
(ill) Semi-detailed soil survey over the areas to be mapped under
(II). Selection and detailed soil survey of about
60,000 acres most suitable in location, topography and
soils for the first development.
(IV) Location and preliminary survey and investigation of
possible sites for storage dams, and for other major works
for river control, such as barrages and canal headworks.
The investigation will include geological studies and,
when necessary, drilling. In the case of storage dams, the
capacities of the reservoirs which they will provide will
be estimated.

-167-.
(V) Hydrologlcal investigations, using all existing data, and also
the additional data to he observed under this Project, covering
the Upper, Middle, and Lower reaches of the river (a) to
estimate what amounts of water can be made available for the
optimum use of the reservoirs found feasible under (IV), for
existing and potential water usages in other reaches of the river,
for irrigation, power and other purposes, such as the need to
control flooding in the Tana Valley, (b) to examine as early as
possible the effect on the regime of the Tana River, of the
proposals for present and future hydro-electric development in
the Basin, with particular reference to the Seven Porks Power
Project, and to suggest to the Kenya Government, if possible
before construction work begins at Seven Porks, any modification
in the development of this site which might lead to improved water
distribution. Close consultation with the appropriate Power
Authority will be necessary during this part of the investigation.
(VI)
(VII)
Taking account of the results of (ill), (IV) and (v), (a), the
assessment of the ultimate potential irrigable area in the Lower
Tana Region and the preparation of an outline plan for its development,
and (b) a preliminary layout plan of the area proposed for
development in the first phase, expected to be about 60,000 acres.
Por both (a) and (b) alternative schemes of agricultural cropping
will be proposed, with estimates and discussions of their respective
economic benefits, as detailed under (IV).
Agronomical studies will cover:
a) land preparation and irrigation practices;
b) research on crops, varieties and their rotations and
their water requirements;
o) methods of cultivation (sowing time, spacing, fertilizers,
pest control, etc.):
d) research on irrigated agriculture on the various types of
soils available in the Project Area, including the. preparation,
equipment and operation of several experimental plots.
(VIII) Technical Assistance to Government in Extending the experimental
work on irrigation already being done on the Pilot Scheme at Galole,
which is being enlarged by Government from 500 to 1200 acres.
(iX) Economic evaluation of potential irrigation development
a) Overall appraisal, lower Tana Basin; crop patterns, for each
available soil type, which will best meet the country's
economio needs. Most suitable sizes and types of farms. Rough
estimates of full potential agricultural production and of cost
of full development, including ancillary expenditure on Research,
Health, communications, etc.
b) Detailed economio assessment of selected 60,000 acres:
Estimates of Project's initial and operational costs for
alternative cropping schemes, with breakdowns by types of work,
by years and by currencies. Estimates of farm costs and
anticipated net farm incomes for each scheme.

-168-
Estimated production by years, expected agricultural benefits,
i-oooinmended governmental extension and credit policies.
(X) In-Service further training of Kenyan counterpart-staff,
in survey and appraisal methods and in modern agricultural
practices will be given a high priority.
(XI) Fellowships! Six one-year fellowships will be granted to Kenyan
specialists for training in the various technical fields covered
by the project.
(XII) Health, problems: In carrying out the investigations described
above under (I) to (X), full account shall be taken of considerations
which may affect public health, particularly in respect of:
(a) the needs of water for domestic supplies as well as those
for irrigation}
(b) the present liability to bilharzia, fascioliasis, malaria,
filaria and generally all water-borne diseases in the
project area, and the probable effects on this of these
diseases consequent upon the development proposed in river
control and irrigation.
In so doing the Kenya Ministry of Health, the Department of Veterinary
Services, and WHO shall be consulted.
II. WORK PLAN
A. Participation and Contribution of the UN Special Fund
3. The Special Fund will provide the following through the Executing Agency:
(l) Exports Man-Years
River Basin Development Engineer
(Project Manager) 3
Civil Engineer (irrigation and Drainage
Layout) 3
Hydrologist 2
Civil Engineer (Location and Design of Dams) 1
Engineering Geologist •§•
Driller
Irrigation Agronomist (Cotton Specialist) 3
Research Agronomist 3
Soil Surveyors (2) 4
Soil Scientist 2
Agricultural Economist 2
Land Surveyors (4) 4
Consultants 1
Total man-years 29 s US$ 570,500
2

-169-
(II ) Fellowships - each for 1 year Man-Years
Irrigation Engineering 1
Hydrology 2
Irrigation Agronomy 2
Agricultural Economics 1 •
Total man-years 6 - US$ 30,000
Fellowships awarded under the Plan of Operation shall be administered in
accordance with the fellowship regulations of the Executing Agency. The Government
shall- continue to pay salaries and allowances for fellows in Government service
during the period of study abroad.
Within the total allocation of $ 30,000 for fellowships, minor adjustments of
individual fellowships may be made, if this is found to be in the best interest of
the project.
(ill) Equipment and Supplies US $
Equipment for trace clearing 22,000
Machinery for irrigation experiments, )
Checkgates, etc. ) 34,000
Pumps, pipes, etc. )
Soil analyses abroad 3,000
Hydrological equipment and pontoon 58,000
16 Landrovers, 2 two-ton trucks and
1 lab. truck 54,000
Camping equipment, including caravan, etc. 33,000
Equipment for soil testing, drilling, )
and experiment work, radio sets . )
Expendable supplies, (seeds, fertil- ) 45»000
izers, insecticides, etc.) not )
available locally )
Printing of maps and reports. 8,000
Total 257,000
The total cost of the equipment will not exceed $ 257,000.
The Project Manager will establish the detailed list of equipment to be purchased
under the above provisions, in consultation with the Co-Manager.

-170-
(IV) Miscellaneous and Contingencies US $
4. Sub-contracts
To cover:
Secretarial assistance )
Postal expenses and cables ) 30,200
Contingencies )
The Executing Agency may provide the personnel mentioned in 3 (i) above, partly
or wholly, through a sub-contract (or contracts) with a firm (or firms) of consulting
engineers acceptable to the Government. Such a sub-contractor may also be asked by
the Executive Agency to arrange, subject to the approval of the latter, the supply
of part or the whole of the equipment to be paid for by the Special Fund, as under
3 (ill) above*. If so, such equipment, though used by the sub-contractor for the
project, will remain the property of the Special Fund until the title to it is
transferred as provided for in paragraph 38 below. A sub-contractor shall assume the
same obligations as those devolved on the Executing Agency under Article II of the
Agreement, referred to in the Preamble to this Plan of Operation. The overall
responsibility for the parts of the Project entrusted to sub-contractors will however
remain with the Executing Agency.
B. Participation and Contribution of the Government
5. Government contribution in kind
(i) Counterpart personnel US $
Technical staff, including assistants for
topographical and soil surveys, hydrology,
engineering, agronomy, etc. for a total
of 308 man-months 154,000
Health assistants, for three years each 14,000
Administrative and service staff 84,000
Drivers, labour and local contracts 50,000
(il) Equipment and Supplies
302,000
Reconnaissance survey, including the
preparation of 1:100,000 maps 25,000
Base lines and mapping, including precision
levelling and reprinting of existing
photographs and maps 25,800
* The purchase of such equipment, when paid for by the Special Fund, will
be subject to the usual FAO rules and regulations for such purchases.

(il) Equipment and Supplies (Cont'd)
-171-
Aerial photography at 1 : 20,000 scale of
approximately 600,000 acres of selected
areas mentioned in para. 2 (i), to be
carried out by the Directorate of
Overseas Surveys, on behalf of the
Government
Special surveys, including dam sites
Agricultural equipment and supplies,
locally available
Operation, maintenance and hire of
vehicles
US $
37,000
20,000
10,000
80,000
197,800
Particulars of the items to be supplied at the cost of the Government will be
decided on by the Executing Agency in consultation with the Government, as soon as the
circumstances permit in each case.
(ill) Miscellaneous
Living and office accommodation and furnishing
for UN and Government personnel and
labour.
Transportation, including insurance,
within the country of personnel employed by
the Executing Agency and by the Government.
Storage, transportation, handling and
insurance within the country of equipment
used for the Project and related expenses.
Research on consumptive use or other
irrigation methods and practices to be
conducted in the project area on existing
irrigation schemes
30,000*
10,000
5,000
75,000
120,000
6. The Government shall issue entry visas to the personnel of the Executing Agency and
of the Executing Agency's contractors employed on the Project.
*Accommodation
1 House Project Manager existing
1 House Co-Manager existing
1 Lie s s Government 8,000
1 Mess PAO. 8,000
1 Office (PAO) Nairobi existing
1 Office (PAO) Galole 5,000
1 Office Government 5,000
Furniture etc. 4,000
Total 30,000

-172-
sucn personnel shall also have the right to the following:
immunity from legal process in respect of: all acts
performed by them in the execution of the project;
immunity from national service obligations;
immunity from immigration restrictions;...
the privilege of bringing into the country reasonable
amounts of foreign currency for the purposes of the.
Project or for personal use of such personnel, and
of withdrawing any such amounts brought into the
country, or, in accordance with the relevant foreign
exchange regulations, such amounts as may be earned
therein by such personnel in the execution of the
project;
and
the same repatriation facilities in the event of international
crises as diplomatic envoys.
7. All personnel of the Executing Agency's contractors shall enjoy inviolability for
all papers and documents relating to the project.
8. The Government shall either exempt from, or bear the cost of, any taxes, duties,
fees or levies which it may impose on any foreign firm or organisation which may be
retained by the Executing Agency and on the foreign personnel of any such firm or
organization in respect of: *
(a) The salaries or wages earned by such personnel in the
execution of the project;
(b) Any equipment, materials and supplies brought into the
country in connection with the Agreement or which, after
having been brought into the country, may be subsequently
withdrawn there-from;
(c) furniture, personal property and household effects (including
one privately owned automobile per employee), imported by
the firm or organisation for its personnel for their personal
use or consumption, in accordance with the terms of the first
arrival privileges agreed between the Government and the
Regional Representative of the UN Technical Assistance Board
as being generally applicable to UN exports.

-173-
9. The privileges and immunities to which such firm or organization and its
personnel may he entitled, referred to in paragraph 6 of this Plan,of Operation,, may
he waived hy the Executing Agency where, in. its opinion, the. immunity would impede .
the course of justice and can he waived without prejudice to the successful completion
of the Project or to the interest of the Special Fund or the Executing Agency. The
Executing Agency shall waive such immunity in any case in which the Managing Director
of the Special Fund so requests.
10. The Executing Agency shall provide the Government with the list of" personnel to
whom the privileges and immunities enumerated above shall apply.
11. Import of Equipment and Supplies
The Government will issue permits for the import free of customs dues of
equipment and supplies.hy the Special Fund of UN for the Project through the Executing
Agency, or will themselves pay the customs charges when the equipment or supplies are
imported.
12. Other Obligations of Government
The Government of Kenya shall furnish the. Executing Agency with such relevant.,
documents, accounts, records,.statements, and other information, as the Special Fund .
may request concerning the execution of the Project, or concerning the compliance by
the Government of Kenya of its responsibilities under this Plan of Operation. After
the completion of the Project, the Government will also make available to the
Executing Agency all information necessary or appropriate to an evaluation of the
benefits derived from and activitie.s undertaken to further the purpose of that project.
13. Local Operating Costs
With reference to the payments to be made by the Government under Article V,
paragraph 1 (a) to (d) of the Agreement referred to in the Preamble.of. this Plan of
Operation, excepting the costs within the country of the storage and transportation
of equipment and supplies for the Project, which are counterpart contributions, the
Government shall pay to the Special Fund, in local currency, the equivalent of
US $ 85,600, towards local operating costs. This amount represents 15$ ..of the total
estimated cost to the Special Fund of foreign project personnel. The equivalent of
the above amount shall be deposited by the Government in local currency to the credit
of the Special Fund account with.the Midland Bank Ltd., 60 Gracechurch Street,
London, E.C.3 (Acct. No. 1039)» in accordance with the following schedule :.
Equivalent of US $ 5,000 on signature of the Plan of Operation
Equivalent of US $ 12,100 on.or before 1st August 1963
Equivalent of.US S 31,800 on.or before 1st January 1964
. Equivalent of US. $ 26,750: on or. before 1st January 1965
Equivalent.of US.$ 9,950 on or before.1st January 1966

C. Organization
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14« Overall responsibility for the organization and execution of the Project rests
with the Executing Agency who shall plan and direct operations through the Project
Manager appointed by the Executing Agency and acceptable to the Government.
15. The Minister of Land Settlement and Water Development will represent the Government
on the Project as far as matters related to Government policy are affected. He
shall appoint a senior technical officer of his Ministry acceptable to the Executing
Agency as Co-Manager.
16. The team of experts of the Executing Agency shall be attached to and work in
close cooperation with the Ministry of Land Settlement and Water Development.
17. All equipment and supplies provided under the Plan of Operation shall be used
exclusively for the execution of the Project during its currency. The movement of such
equipment and supplies shall come under the authority of the Project Manager.
18. The Project Manager, under the general supervision of the Executing Agency, shall
be responsible for the detailed planning, administration and execution of the Project,
including timing and budgeting of the various elements, the preparation of technical
reports, and the organization and supervision of related training programs. In
undertaking these responsibilities the Project Manager shall work closely with the
Co-Manager.
19« The Ministry of Land Settlement and Water Development shall ensure co-ordination
of the work of governmental and other organizations which may be called upon to participate
in, or carry out, work related to the Project.
20. Selection and employment of counterpart personnel and of candidates for fellowships
shall be made jointly by the Project Manager and Co-Manager.
D. Sequence of Operations
22. The Executing Agency shall begin execution of the Project upon receipt of written
authorisation to do so from the Managing Director of the Special Rind.
23» Immediately after the Project becomes operational the Executing Agency shall
proceed with the employment of experts as foreseen in Paragraph 3 of this Plan of
Operation and shall place orders for vehicles, equipment and supplies required for the
Project. If it is decided to carry out part or all of the Project by sub-contract
with a consulting firm, the Executing Agency shall select and submit to the Government
the names of a limited number of consulting firms which it wishes to consider for
employment on the Project. After receiving clearance from the Government for the
employment of any of these consulting firms, the Executing Agency shall initiate
negotiations with them, and after selection of the most favourable offer, will
conclude a contract accordingly for the part of the work to be carried out by subcontract.

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24. Upon the arrival of the Project Manager in Kenya, the Government shall take
immediate steps to appoint the Co-Manager, to assign to the Project the necessary
counterpart and other personnel and labour, to make available the necessary services,
and to place orders for equipment and supplies to be provided by Government, all in
accordance with the terms of'this Plan of Operation. The date of arrival of the fully
appointed Project Manager in Kenya will be taken as the date from which the period of
the project will be measured.
25. A detailed Work Plan for the first year of operation of the Project will be
prepared by the Project Manager in collaboration with the Co-Manager, within two
months of the arrival of the Project Manager in the country or the appointment of
the Co-Manager, whichever is the later. Similar Work Plans shall be prepared each
year by the Project Manager in collaboration with the Co-Manager not later than
1st December, to cover the following year. These V/ork Plans shall include overall
schedules for the project operations, detailed lists of equipment, supplies and
materials to be purchased, staffing plans, and arrangements for transport and other
services.
26. Within tv/o months of the signature of the Plan of Operation, the Government shall
make available to the Executing Agency two sets of all existing aerial photographs,
photographic lay-downs, and topographical survey maps covering any part of the basin
of the Tana River, as well as all existing reports and documents relevant to the
Project.
27. Within one month of his arrival in Kenya, the Project Manager shall, in collaboration
with the Co-Manager, initiate the collection of existing data, reports and other
information, and the starting of preliminary studies. These will follow the first
general reconnaissance of the project area, to cover the main aspects of the project,
including topography, hydrology, soils, existing land use, forest, grasslands and crops.
On the results of this reconnaissance will be selected the areas for basic levelling
and mapping and for semi-detailed soil survey, as described in paragraph 2 (il) and
(ill). At the same time will be selected the potential site for storage reservoirs,
dams, and other major works, to be surveyed on larger scales and examined more
closely, as described in paragraph 2 (TV). Hydrological investigations, including
the location and installation of any additional gauging stations necessary, will also
be initiated, in accordance with paragraph 2 (v) above.
28. As soon as progress with the various surveys and investigations makes it possible,
the total area which is potentially irrigable in the Lower Tana in respect of topography,
soils, water, and agricultural economics, will be determined, and from this
area will be selected a part, expected to be about 60,000 acres in extent, to be
proposed for development in the first phase. More detailed studies, planning, and
estimates for this part will then be carried out, in accordance with paragraph 2 (Vi)
to (IX) above.
29. A tentative timetable showing the timing of employment of the various specialists
is given in the diagram below; this will be subject to review and modification,
within the total or man-years of export services, with the preparation of each successive
Work Plan. The commencement of operations is cheduled for 15th May 1963.

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Specialist . 1963 1964 1965 1966
Bàsin Development Engineer
Civil Engineer - Irrigation and
Drainage layout
Hydrologist
Civil Engineer — Dams
Engineering Geologist
Driller
Irrigation Agronomist (Cotton
Specialist)
Re search.Agronomist
Soil Surveyors
Soil Scientist
Agricultural Economist
Consultants
Land Surveyors
• -
? 7 ? •• ?
? •• ?
30. During the course of all surveys and investigations, every opportunity will
be taken to train further the Kenya counterpart personnel. Training will include
lectures, laboratory or drawing office work (where applicable) and field work. Details
will be decided by the Project Manager and Co-Manager in consultation with the
specialists concerned in each particular case.
31. Candidates for fellowships will be selected by the Project Manager and Co-Manager
jointly as soon as possible in the course óf the training programs= After completion
of their fellowship studies they will be engaged on the work of the project in their
respective fields, bearing increased shares of responsibility according to their
abilities.

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III • BUDGET
32'.' In. addition to the' services and facilities described in paragraph 5 -above', which
shall be provided in kind to the. project by ,the Government and estimated to cos 1 !; an
amount of E.A. Shillings" equivalent to US '$ 619,800 as detailed in Appendix II,
the estimated total cash project budget amounting to. the equivalent of US $ 974,100.
will consist."of. the following:
(a) the gross cost of exports, fellowships, contractual services,
equipment and miscellaneous expenses, described in paragraph'3
, above to be met by the Special Fund and amounting .to an estimated
- ; total of US $ 887,700 which includes an amount estimated at the
equivalent of US $ 85,,600, "representing ,cash payments in local \
currency tto be made by the Government to the Special Rind towards ;
local operating costs described in paragraph 13 above (see "
Appendix I)
(b) the overhead costs of the Executing Agency US $ 86,400 to be met
by the Special Fund (See Appendix i).
IV REPORTS
33« The Executing Agency shall submit to the Government the following reports on the
Projeot:
(a) an Inception Report, to be supplied not more than 6 months after
the initiation of the project,"'containing the/results of the
preliminary reconnaissance surveys arid propo'saTs on the further
planning of the Project;
(b) an Annual Report to reach the . Government by/ï,lïarch each year,
covering the period of the previous calendar year;
(c) a Mid-year Report to reach the Government by 1 September each
year, covering the work up to 30 'June of that'year; and
(d) a Final Report after the project has ended.
34« The Government shall submit to the Executing Agency annual progress reports at the
end of each year and a final report at the conclusion of the operation-of-the Project.
35» The Government and the Executing Agency jointly shall submit to the .Special Fund
at the end of each calendar year a certified inventory of equipment purchased"with the
funds allocated by the Special Fund.

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V CONCIPSIONS
36. Upon completion of the Project, a report will be submitted by the Government to
the Executing Agency and the Special Fund on the benefits derived from the project
and the activities planned by the Government to further the purpose of the projeot.
37« After the completion of the Project, the Government undertakes to continue
research programs and investigations on all major aspeots of the Project which will
have been studied during its course, so far as it may find these feasible in the
circumstances of the time.
38. At the successful conclusion of the Project, the Government, the Executing
Agency and the Special Fund, will consult with a view to transferring the title to
the equipment from the Special Fund, in whose name it has been held by the Executing
Agency, to the Government or an Agency nominated by the Government«
Agreed on behalf of the parties by the undersigned«
For the Government of Kenya For the UN Special Fund
N. S. Carey Jones George Ivan Smith
Permanent Secretary - Ministry
of Land Settlement and Water
Development
Date 11 April 1^63 Date 2 May 19.63
röx' tlio uOvoi'iuuônt öi. A.enya
Jomo Kenyatta
Date 2 April 1963
For the Food and Agriculture
Organization of the UN
Norman C. Wright
Deputy Director-General
Date 2 April 1963

Project Managers
Project Co-Managers
Irrigation Engineers
Hydrologist Engineer
Dam Engineer
Geologist
Senior Soil Surveyors
Soil Surveyors
Soil Chemists
Research Agronomist
Cotton SpeoialistB
Irrigation Specialist
Economist
Administrative Offioers
Chief Draftsman
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LIST OP PROJECT STAFF
R.W. Walker/C. Freyburg
I.D. ¥atts/G. Manig
H.D. Ayers/J. De Wolf
J.B. Kirch
G. Mitchell
L. Holofsky
APPENDIX II
J. Schilstra/K. van de Meer
K. Tanis/F. Voncken/T. Pompen
A. Muller/H.A. Leyder
G.A. Kan
L. Bannink/Q.J. Kerkhouen
C.U. Freyburg
V.J.M. Joosten
V.R. Kibble/R. Marshall
R.H. Randall

Name
Alex Augustine Ojwang
Vijay Kumar Duggal
Pravinehandra Juthalal
Shah
Prawin D. Shah
Jilo Francis Saiseli
A.M. Benjamin
S.S. Yako
-i8ó-
FELLOWSHIP AWARDS
Field of Study
APPENDIX III
Countries
of Date Date
Study Begun Concluded
Irrigation Agronomy and Sudan 20.9.65 19.3.66
Agricultural Production
Irrigation Engineering
Hydraulic Structures
Hydraulio Engineering
U.S.A. 22.2.65 5.IO.66
Canada
U.S.A. 16.5.65 22.6.66
Canada
Nether- I7.IO.65 21.9.66
lands
Irrigation Scheme Menage- Sudan 1.10.65 18.5.66
ment Israel
Irrigation' Agronomy
Irrigation'Agronomy
Israel - 1*7.66 25.9.66
Israel i.7*66 25.9.66

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REFERENCES
APPENDIX IV
1. Climatic Seasons of East Africa. Pamphlet Series No. 8, East African Meteorological
Department, January, 1962.
Z» The Natural Resources of East Africa. Edited "by É.W. Rüssel, East African
Literature Bureau, June, 1962.
3. Shape of the Submiocene Erosion Land in Kenya. W. Pulfrey, Bulletin No. 3,
Geologic Survey of Kenya, I96Ö.
4. A Preliminary Report on a Survey of the Fisheries of the Tana River, Kenya.
M.J.' Mann, East African Freshwater Fisheries Resëaroh Organization, April,
1966. ••-'•"• - - . - ' - .
5. Unpublished filési BP-Shell Petroleum Development Company of Kenya, Ltd.
Mombasa.
6. Report Nó. 15. F. Diiëy, Geological Survey of Kenya., 1948.
7. The Geology and Mineral Resources of Kenya (revised). W. Pulfrey, Geological
Survey of Kenya, Bulletin No. 2, i960. (A more up-to-date and detailed aocount
of Kenya's mineral resources was in press in April, I966, and should he"
available from the Geological Survey of Kenya in the near future).
8. The Geology of East Africa. E.P. Saggerson, the Natural Resources of East
Africa, edited by E.W» Russell. East JLfrioän Literature Bureau, 1962.
9. East Afrioan Plateaux and Rift Valleys* B. Willis, Carnegie Institute of
Washington, Studies in Comparative Seismology, Noi 470, 1936« .
10« Soil Classification, A Comprehensive System, Seventh Approximation. United
States Department of Agriculture, I960.
11. Development Plan, 1965-1970. Government of Kenya.

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12. The Natural Resources of East Africa. Edited by E.W. Russell, Kenya, June,
i?62.
13* upper Tana Catchment Water Resources Survey. Government of Kenya, Sir A. Gibb .
and Partners (Africa), Kenya, April, 1959«
14* Reassessment of Seven Forks Hydro-electrio Project, Kenya. Pover Securities
Corporation Ltd., Balfour, Beatty and Company, Ltd., London, August, 1964*
15» Seven Forks Hydro-electric Projeot. East African Power and Lighting Company,
Ltd., Balfour, Beatty and Company Ltd., London, August, 1964.
16. Survey of the Irrigation Potential of the Lower Tana River Basin, Kenya.
Interim Report,- Advance Information on Seven Forks Storage and Operation,
FAO, July, I965.
17. Survey of the Irrigation Potential of the Lower Tana River Basin, Kenya.
Interim Report, FAO, September, 1965*
18. Seven Forks Hydro-electrio Project, Reservoir Development, Geology Report.
East African Power and Lighting Company Ltd., Balfour, Beatty and Company Ltd.,
London, February, 1962*
19« Seven Forks Hydro-electrio Project, Gtaru Development, Geology Report. East
African Power and Lighting Company Ltd., Balfour, Beatty and Company Ltd.,
London, June, 1963*
20. Seven Forks Hydro-electric Project, Kindaruma Development, Geology Report.
East African Power and Lighting Company Ltd., Balfour, Beatty and Company Ltd.,
London, June, 1963*
21. Estimates of Maximum Demand and Memorandum on Plant Provision, 14th Edition.
East African Power and Lighting Company Ltd., Nairobi, Hay, 1963.
22. Report on Harket for Electricity. East African Power and Lighting Company Ltd.,
Merz and McLellan, London, February, 1964«
23. Reassessment of Seven Forks Hydro-eleotrio Development Plans submitted with
Water Permit Application. Power Securities Corporation Ltd., Balfour, Beatty
and Company Ltd., London,. May, I960«
24. Seven Forks Project, Kenya. Notes on Economic Irrigation Storage at Seven Forks
(revised). Tana River Development Company Ltd., Balfour, Beatty and Company
Ltd., London, March, 1965*
25« CA.TIA/H aw Power Develops!ent Concept-s — A Challenge. T.R. Anand, E.I.C. Journal,
May, 1965.
26. Gezira - A Story of- Development in the Sudan. Arthur Gaitskell, Fab er and
Fab er, London, 1959.