SubSurface Dams - Sustainable Sanitation and Water Management ...

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Department of the Environmentand Framework of Life ofBurkina Faso(Formerly the Department of theEnvironment and WaterGlobal EnvironmentalIssues Division in Ministryof the Environment ofJapanAdvisory Committee on theModel Project to CombatDesertificationNational Council for theEnvironment and DurableDevelopment (S.P.CONEDD)(Formerly the National Councilfor Management of theEnvironment) (S.P.CONAGESE)Overseas EnvironmentalCooperation Center(OECC)TAISEI CORPORATIONMU (µ) GIKEN CO., LTDOther governmentalorganisations and localauthorities in BurkinaFasoVillagersin Nare andKombangedo VillagesResearch organisations,contractors, privatecompanies and NGOs inBurkina FasoFig. 1.1: Organizational framework of the project7
1-4 Outline of the facilities for the demonstration studiesThe facilities for the demonstration studies in this project were as follows:(1) Subsurface damA subsurface dam with the following characteristics was constructed on the Kolongo River atthe Koulikare Quarter in Nare Village:Type: earth damCrest length: about 210 mDepth of dam: 3.0 to 11.4 m (maximum) below the ground surface(2) Other experimental facilities- Water-pumping station operated by solar energy: with 3 water-pumping wells (about 20-mdepth) located in the reservoir area, with 1.76 kwp of solar power- Multi-purpose water-supply stations: water-supply stations for domestic, agricultural andlivestock uses- Pilot farm: 0.25-ha area, located in Kombangbedo Village for cultivation tests of cerealsand vegetables by methods such as drip irrigation- Small-scale surface dam with water gates: 33-m width with 23 water gates, maximumwater level being 1.2 m, utilizing the bridge piers of a main road located 1.2 km upstreamof the subsurface dam site to recharge groundwater(3) Facilities for groundwater observation- Facilities for groundwater observation with automatic water level recorders: at 5 points(The water level recorders were removed in 2001 due to decrepitude.)- Wells for groundwater observation: 3 boreholes and 2 large-diameter wells- Wells for water pumping and groundwater observation: 2 boreholes and 4 large-diameterwells- Sets of piezometers (wells for observation of the hydraulic head): 16 pipes located at 4points(4) Meteorological stations (mainly of rainfall)- Meteorological station in the Koulikare Quarter in Nare Village: a station for theobservation of rainfall, evaporation, temperature, humidity, etc.- Rainfall stations in the Kolongo River basin: 3 stations (the Kossonkore Quarter in NareVillage, Ouanobian Village, and Noka Village)1-5 Evaluation of the results of the project and prospects(1) Water storage stateThe subsurface dam constructed in this project stores water in the reservoir layer consisting of"fossil valley sediment" and heavily weathered basement rock. According to the calculationusing a simplified reservoir model, the extent of the reservoir area, the groundwater level andthe volume of the reservoir at its maximum storage capacity are as follows:- Width of the reservoir area: about 150 m (lowest estimate)- Length of the reservoir area (upstream distance to which the reserved water extends): 13.4km- Maximum groundwater level: -3.0 m (depth below the ground surface)- Water storage capacity: about 1,800,000 m 3 (with the effective porosity of the reservoirlayer estimated to be 20%)Up to the end of 2002, the groundwater level (depth below the ground surface) varied from-7.0 m at the end of the dry season to -4.2 m at the end of the rainy season, and had not yetreached the maximum level. The reservoir area probably extended 5 or 6 km upstream ofthe dam, and the volume of reserved water was thus estimated to be about 400,000 m 3 at theend of 2002.8
Page 2 and 3: Photo: Construction of the subsurfa
Page 4 and 5: Subsurface DamSmall-Scale Surface D
Page 6 and 7: ContentsIntroduction1. General desc
Page 8 and 9: 1. General description of the Model
Page 12 and 13: According to the results of an anal
Page 14 and 15: A large amount of waterevaporates f
Page 16 and 17: y adopting an appropriate dam struc
Page 18 and 19: 2-5 "Fossil valley", a suitable sit
Page 20 and 21: temperature of 30 to 34 degrees and
Page 22 and 23: 3-3 Distribution of fossil valleys
Page 24 and 25: 3-4 Surveys carried out in this pro
Page 26 and 27: Satellite image of the area around
Page 28 and 29: 3-4-2 Field explorationAt the 5 sit
Page 30 and 31: 3-4-3 Geophysical surveyAt the 5 si
Page 32 and 33: Groundwater level assumed from the
Page 34 and 35: 3-5 Detailed field surveys (test dr
Page 36 and 37: Groundwater level isalmost the same
Page 38 and 39: The village is on a peneplain with
Page 40 and 41: In this project at Nare, the "earth
Page 42 and 43: DownstreamFilled back soil3mCoarseg
Page 44 and 45: All the results of the quality test
Page 46 and 47: Photo 4.3: Construction of the subs
Page 48 and 49: 4) Basal stratum of the fossil vall
Page 50 and 51: 6. Observation of the water storage
Page 52 and 53: Table 6.1: Features of the faciliti
Page 54 and 55: PerchedwaterImpermeablelayer“Main
Page 56 and 57: Table 6.3: Annual rainfall in the K
Page 58 and 59: 3) The reserved water level during
Page 60 and 61:
Ground surface level: 275.73mGround
Page 62 and 63:
6-4 Analysis of seasonal fluctuatio
Page 64 and 65:
SandysiltSiltSand(white)Sand(moist)
Page 66 and 67:
(1) Relation between the rainfall w
Page 68 and 69:
4) Subsequently, the cycle in which
Page 70 and 71:
7. Other studiesIn addition to the
Page 72 and 73:
these facilities:- 3 mill stations,
Page 74 and 75:
Photo 7.3: Water-supply station for
Page 76 and 77:
8. Recommendations for future subsu
Page 78 and 79:
advisable to arrange rainfall stati
Page 80:
AcknowledgementsThe Model Project t
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