construction and refurbishment of earthen irrigation channel banks
construction and refurbishment of earthen irrigation channel banks
construction and refurbishment of earthen irrigation channel banks
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21. Channel SeepageTable <strong>of</strong> ContentsSubjectPage No.21.1 Introduction ........................................................................................................... 21-321.2 Seepage from Channels.......................................................................................... 21-321.3 Factors Affecting Seepage ..................................................................................... 21-421.3.1 Permeability..................................................................................................................................... 21-721.3.1.1 Hydraulic Conductivity (K)............................................................................................................ 21-821.3.2 Effect <strong>of</strong> Channel Geometry on Seepage ......................................................................................... 21-821.3.3 Hydraulic Gradient........................................................................................................................... 21-821.3.4 Water salinity................................................................................................................................... 21-921.3.5 Variation over Year.......................................................................................................................... 21-921.4 Channel Seepage Consequences........................................................................... 21-1021.4.1 Loss <strong>of</strong> the Water Resource ........................................................................................................... 21-1021.4.2 Cost to Irrigation Authority............................................................................................................ 21-1021.4.3 Cost to Adjacent l<strong>and</strong>owners ......................................................................................................... 21-1021.4.4 Regional Consequences ................................................................................................................. 21-1121.5 Channel Seepage Measurement............................................................................ 21-1221.5.1 Seepage measurement units ........................................................................................................... 21-1221.6 Estimation <strong>of</strong> Seepage from Proposed Channels................................................... 21-1321.6.1 Measurement <strong>of</strong> Soil Hydraulic Conductivity (K) ......................................................................... 21-1421.6.1.1 Measuring hydraulic conductivity above the watertable .............................................................. 21-1521.6.1.2 Measuring hydraulic conductivity below the watertable.............................................................. 21-1621.6.1.3 Laboratory methods <strong>of</strong> measuring permeability........................................................................... 21-1721.6.2 Channel Seepage Modelling .......................................................................................................... 21-1721.6.2.1 Analytical Models ........................................................................................................................ 21-1921.6.2.2 Process Models............................................................................................................................. 21-2021.6.2.3 Calibration <strong>of</strong> Models................................................................................................................... 21-2121.6.2.4 Accuracy <strong>of</strong> Models ..................................................................................................................... 21-2221.7 Measurement <strong>of</strong> Seepage from Existing Channels................................................ 21-2221.7.1 Seepage Studies ............................................................................................................................. 21-2221.7.2 Measurement techniques................................................................................................................ 21-2421.7.3 Direct Measurement....................................................................................................................... 21-2521.7.3.1 Pondage Method (static seepage test)........................................................................................... 21-2521.7.3.2 Inflow-Outflow Method (Dynamic Seepage Test) ....................................................................... 21-2821.7.3.3 Seepage Meter Method................................................................................................................. 21-2921.7.4 Indirect Measurement .................................................................................................................... 21-3121.7.4.1 Piezometric Surveys ..................................................................................................................... 21-3121.7.4.2 Geophysical Techniques............................................................................................................... 21-3221.7.4.3 Hydrochemical Tracers ................................................................................................................ 21-3321.7.4.4 Remote Sensing Techniques......................................................................................................... 21-3421.8 Seepage Remediation Techniques ........................................................................ 21-3421.8.1 Bank Refurbishment / Re-<strong>construction</strong>.......................................................................................... 21-3521.8.2 Core Trenching .............................................................................................................................. 21-3521.8.3 Re-compaction ............................................................................................................................... 21-3621.8.4 Channel Lining............................................................................................................................... 21-3721.8.5 Sediment Sealing ........................................................................................................................... 21-3721.8.6 Surface interception drainage......................................................................................................... 21-3821.8.6.1 Surface drains at toe <strong>of</strong> bank ........................................................................................................ 21-3821.8.6.2 Regional Drainage Systems.......................................................................................................... 21-3821.8.7 Interception Drainage..................................................................................................................... 21-3821.8.8 Groundwater interception .............................................................................................................. 21-3821.8.9 Tree Planting for Seepage Interception.......................................................................................... 21-39Construction <strong>and</strong> Refurbishment <strong>of</strong> Earthen Channel Banks August 2002 – Edition 1.0 21-1