construction and refurbishment of earthen irrigation channel banks

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ainfallPumpingevapotranspirationIrrigationinfiltrationGroundwaterChannel SeepageOUTFLOWExchange with lower aquiferINFLOWFigure 21-3Flows through a control volumeGroundwater flow model uses include:• estimate what seepage will occur from a proposed channel• estimate what seepage will occur after rehabilitating an existing channel, or• assess a range of seepage remediation techniques for an existing channel.• evaluate the effect of different geological layers under and adjacent to the channel• evaluate the effect of channel shape; ie width, depth, slopes of batters• evaluate the effect of vegetation adjacent to the channel• evaluate the possible benefits of remedial measures, eg lining• evaluate field measurements of seepage relative to soil permeability andgroundwater levels• evaluate what proportion of accessions to the groundwater are from channels asagainst other sources• evaluate the effect of channel seepage on regional or sub-regional groundwatersystems• estimate channel seepage volumes without direct measurement.In Australia the modelling of channel seepage is not practiced routinely. This mayindicate a lack of faith that modelling will be useful, or a belief that the costs aretoo high relative to the gains in knowledge.Modelling of channel seepage flow is complicated due to the factors below:• channels of irregular cross-section• natural processes in the channel of erosion, sedimentation, biological action etc.• non-uniformity of sub-soil in horizontal as well as vertical extent• variation in evaporation rates and capillary rise throughout the year• changing elevations of the water surface in the channel• changing elevation of the watertable• the effect of the chemistry of the channel water on the hydraulic properties of thesoil. This causes hydraulic conductivity to change in time as well as in space.the hydraulic conductivity is also affected by the air content of the soil.Construction and Refurbishment of Earthen Channel Banks August 2002 – Edition 1.0 21-18
• the degree of saturation of the sub-soil. Complete saturation, even below thewatertable, is the exception rather than the rule. The volume of entrapped airbelow the watertable can vary with time, depending on the air content and thetemperature of the channel water, the temperature of the soil, and barometricpressure. Unsaturated conditions also occur where the soil-water pressures areless than atmospheric.• salt transferral up through the soil layersVarious modelling techniques can be used to simulate groundwater movement,ranging from simple analytical models to complex process models. Thecomplicated dynamics of the seepage process are very difficult to represent with amathematical equation. To accommodate all of these variations a fairly complexnon-steady state model is needed. However where the flow systems and theevaporation process may be simplified, an analytical model may provide solutionsof sufficient accuracy.21.6.2.1 Analytical ModelsDarcy’s LawDarcy’s Law is a simple equation which can be used to estimate seepage.According to Darcy’s Law the velocity of flow through water-bearing sand isdirectly proportional to the head consumed. This law is generally assumed toapply to all saturated water-bearing materials in which the pores are of capillarysize and the flow is laminar.Q = K x A x h /lWhere,Q = quantity of water in unit time (m 3 /day)K = hydraulic conductivity of the soil (m/day)A = wetted area of the channel bed and banks (m 2 )h /l = the average hydraulic gradient in the close vicinity of the channel.(m/m)h = change in potential energy (head) of water between two locations (m)l = distance in seepage water has travelled between two locations (m)Advantages:Simple and quickLimitations of Darcy’s Law:• Difficulties in measuring average saturated hydraulic conductivity betweenthe channel wetted perimeter and the groundwater• Lack of spatial information on the variation in hydraulic gradient betweenthe channel and groundwater.Construction and Refurbishment of Earthen Channel Banks August 2002 – Edition 1.0 21-19
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Your comments on the format and con
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During the course of this project,
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AcknowledgmentsThese Guidelines rep
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FundingFunding of this project was
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Table of ContentsBook 1SubjectPage
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1. Introduction1.1 GeneralGood asse
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(iv) provide proven practice approa
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3. Research Procedure3.1 Terms of R
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4. How to use these Guidelines4.1 W
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6. Units of MeasurementQuantity Uni
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8. Earthen Irrigation Channels8.1 D
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8.3 ReferencesAustralian National C
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9.1 IntroductionA key input to adva
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Data from Goulburn-Murray Water’s
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General 1 2 3 4 5 6DescriptionRisk
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Channel BankSequential Deterioratio
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9.2 ReferencesGutteridge Haskins &
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10.2.3.1 Dispersive layer of materi
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Causes ofSpecific factorDeteriorati
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10.1.2.5 BendsA bend in the channel
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10.1.4.1 Construction techniqueIrri
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10.1.5.4 Overtopping of banksIn ade
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In the past maintenance techniques
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Maintenance is a continuing require
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10.1.7.4 Yabbies/fresh water crayfi
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Direct removal ofmaterial by entrai
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Figure 10.10 shows longitudinal cra
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10.2.3.3 Irregular compaction - bri
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10.3 ReferencesEmerson W (1996), pe
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11.1 GeneralThe Investigation and P
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iv) Available fill materials and, w
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12.15 Radius of Bends .............
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There are several ways a channel ca
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• Land acquisition extent and typ
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The investigation should generally
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• Backfill: 10% compaction factor
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1. Flow Area, A, is the cross-secti
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after ageing and weed growth. If an
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elationships may be the controlling
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These maximum velocities should be
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Thus channels are usually designed
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Some of the design issues that shou
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12.12.1.3 Best PracticeEither of th
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12.13.2 Channel MaintenanceIncrease
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along a channel. The depth of the w
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12.13.4.7 Change of AlignmentThe in
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12.15 Radius of Bends12.15.1 Flow A
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12.16 Channel Cross SectionThe cros
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Some irrigation authorities use one
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12.16.2 BanksChannel cross sections
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Unless the bank is very high, the s
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The stability of channel batters ca
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drop bars become difficult and time
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Both the height above the bed and t
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• enable maintenance of the chann
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- Access agreementsA description of
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13/08/02 19:2012.20 Channel Tenure
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13/08/02 19:20As with the damage to
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13/08/02 19:20Advantages of Protect
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- gates provide a better deterrent
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13/08/02 19:20When considering expo
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13/08/02 19:20A typical design draw
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13/08/02 19:20Sinclair Knight Merz
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13.1 IntroductionIn many irrigation
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For example, the initial constructi
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13.2.6 When to use Life Cycle Analy
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The timing of the life-cycle costin
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• assess cost of collecting missi
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Microsoft Excel has quite a good pr
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The costs used in these methods sho
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Life CyclePhaseInvestigationDesignC
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Life CyclePhaseMaintenanceRehabilit
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ReplacementProject managementInvest
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Residual valueLegal feesInsuranceAd
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13.4.6.2 Recurring CostsChannel con
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$1.00.80Percent ofValue of$1.00.60.
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13.4.11 Evaluate ResultsThe results
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13.6 Tipsthe way open to incur sign
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14. Risk AnalysisTable of ContentsS
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Consequences for irrigation authori
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15. Material Selection and TestingT
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c) Shrinkage - will the bank crack
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depth. For this reason, the soils o
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Natural moisture content should als
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The study identified some confusion
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15.4.2 Determination of the plastic
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1. Preparation of PatTake approxima
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EmersonClass No.Degree ofDispersion
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15.7.1 Coarse grained soilsIn this
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sufficient gravel for erosion resis
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GroupSymbolsSuitability for Earthen
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The uniform application and thoroug
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essential that the chemical is thor
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Where laboratory testing facilities
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Clays are the plastic fines. They c
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etween the soil sample and the wate
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16. Compaction ControlTable of Cont
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16.1 PurposeDuring this research pr
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All compaction equipment utilises s
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The soil density required for a cha
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In the past, a method specification
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Low permeability and high stability
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16.10.1.1 Tamping Foot RollerTampin
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16.10.1.5 Non-Circular Impact Rolle
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16.10.3 Compactor OperationsAfter t
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16.11.4 Moisture Content ControlBef
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16.12 Density Control Tests and Pro
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Correlation with local materials an
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The main advantages of the Nuclear
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Figure 16.4Hilf Density Ratio Repor
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The location and test results for e
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16.14.3 Reporting and RecordsTest r
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16.16 Tests for small projectsThe s
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The advantages of the Drop Test are
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AS1289.6.3.2-1997AS1289.6.3.3-1997A
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17. Protective CoverTable of Conten
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The bank dries and cracks from the
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17.5 Specifications17.5.1 GravelPar
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17.6 Establish Vegetation CoverTops
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Species Growing Conditions Establis
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17.7.2 Rope Wick ApplicationMuch of
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There are a number of fibre mats or
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17.10 Australian StandardsAS1289.3.
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18.1 IntroductionFor many earthen c
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When re-shaping the batters of exis
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LifeCrestOld bank lineBattered bank
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Photos\inside batter\CG7channel2arm
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4. To help place the rock material
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False ToeFigure 18.8Protective laye
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The confinement system would be adv
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• Able to survive during non-oper
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18.6 ReferencesHutchison D & Locke
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19.20 Guidelines on Field Quality C
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Construction and Refurbishment of E
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• Figure 19.2)3. Temporary Bench
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The capabilities and limitations of
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19.3.1 Construction EquipmentThe ba
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construction. The aim of scarifying
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Page 284 and 285: distribution. The use of alternativ
Page 286 and 287: 19.8 Construction RecordsAdequate r
Page 288 and 289: 19.12 Protective Cover on Crest and
Page 290 and 291: 19.21 Australian StandardsAS 1726-1
Page 292 and 293: 20.1 ScopeAustralia’s earthen irr
Page 294 and 295: Bank re-construction normally requi
Page 296 and 297: •meter outlet locations and type
Page 298 and 299: In the case of channel bank refurbi
Page 300 and 301: 20.4.1.1 StrippingWith outside bank
Page 302 and 303: All public roads to be used by truc
Page 304 and 305: 5. Material is delivered by trucks
Page 306 and 307: Need to drain and de-waterEBM befor
Page 308 and 309: significantly and a more conservati
Page 310 and 311: Aim for crest width ofabout 2 metre
Page 312 and 313: Refer to Section 18, Inside Batter
Page 314 and 315: 21.8.10 Re-alignment ..............
Page 316 and 317: Seepage is a complex hydrologic phe
Page 318 and 319: 2. Seepage losses increase as the d
Page 320 and 321: Refer also to the following section
Page 322 and 323: 21.4 Channel Seepage ConsequencesSe
Page 324 and 325: Channel seepage is one of the sever
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Page 328 and 329: Methods based on vertical flow meas
Page 332 and 333: Flow NetsA flow net is a system of
Page 334 and 335: Data from indirect measurement proc
Page 336 and 337: (ii) EM SurveyElectro-magnetic (EM)
Page 338 and 339: The volume of waterloss from the dr
Page 340 and 341: 21.7.3.2 Inflow-Outflow Method (Dyn
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Page 346 and 347: Stable IsotopesThe basis of testing
Page 348 and 349: To be most successful, there needs
Page 350 and 351: 21.8.6 Surface interception drainag
Page 352 and 353: KeyWatertable before tree plantingW
Page 354 and 355: • The preparation of a best pract
Page 356 and 357: 21.11 ReferencesAustralian National
Page 358 and 359: 22. Channel LiningTable of Contents
Page 360 and 361: 22.1 IntroductionThe conservation o
Page 362 and 363: The different types of channel lini
Page 364 and 365: Table 22-1Unlined Earthen Channels
Page 366 and 367: Lining of channels will not elimina
Page 368 and 369: To supply a given discharge, the cr
Page 370 and 371: 22.4.5 Structural SafetyThe stabili
Page 372 and 373: soil pressures and under-drainage i
Page 374 and 375: Concrete linings are suitable for b
Page 376 and 377: 22.5.12 Availability of Constructio
Page 378 and 379: esistance to erosion. To improve th
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Construction and Refurbishment of E
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22.7.1.2 General Design Considerati
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22.7.1.4 Lining ThicknessThe thickn
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particular problems, but in smaller
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Where the earth lining finishes abo
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control where the channel material
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sand requires about 5% cement by we
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22.7.6 Soil SealantsSoil sealants a
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22.7.7 Cost of Earth LiningsThe cap
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Although they can assist with shear
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22.8.2 Membrane Liner TypesGeomembr
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Polyethylene has also appeared in m
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FPP resistance to common chemical e
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The base coat and seal coat rates m
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A common and misleading argument is
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These thermal expansion and contrac
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Another factor is the ability to ha
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Some lining methods expand and cont
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22.8.9.1 Geomembrane ThicknessThe t
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Cover typeThickness ofEarth fill(m)
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22.8.9.5 Cover MaterialGeomembranes
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As well, velocities which are permi
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22.8.11 FencingWhen livestock, part
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22.10 ReferencesAlther GR (1987), T
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23. Measures to Reduce the Rate ofD
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Channel DesignBank MaterialDeterior
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Stock and VerminAdjacentlandholders
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To ensure that a channel bank has a
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Advantages of Draining• Allows fo
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To efficiently maintain a channel,
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Compared with other countries where
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23.4.7 LeaksTransverse cracks are t
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23.5 Reduction of Deterioration due
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Photo 23-1Channel bed showing mumbl
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Thus, control of carp by draining c
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The disadvantages of a biological c
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Carp have been blamed for erosion o
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Management Groups gives guidelines
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Organisation Contact Details Aims/A
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Chemical treatment is often recomme
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23.7 Reduction of Deterioration due
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Grey Parrot Pea - Dillaynia cineres
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Lodge G (1998), Review on Fish Barr
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cation exchange capacity (CEC) a me
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fetch the distance over which the w
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plant term used for construction eq
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supply level the supply level is a
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