GROUNDWATER-FLOW MODELING OF DEEP INTERCEPTOR AND GRID DRAINAGE FOR INTERCEPTION OF CANAL SEEPAGE AND GROUNDWATER

A groundwater-flow study was initiated to compare the relative effectiveness of deep interceptor and grid drainage to intercept seepage from irrigation canals. Four experimental sites, representing different hydrogeological conditions, were selected for this study. Evaluation methods included test drilling, the installation, testing and monitoring of piezometers and watertable wells and mathematical modeling of groundwater flow. Results of a one year groundwater monitoring program were used to calibrate the groundwater-flow model, MODFLOW. Subsequent simulations indicated that grid drainage and deep-interceptor drainage would provide equal control of the watertable where land downslope of the irrigation canal was affected mainly by canal seepage. Where seepage and groundwater influenced downslope land, grid drainage provided better watertable control than deep-interceptor drainage. Flow simulations using an irrigation recharge to enhance leaching of excess soil salts, indicated that grid drainage would provide better watertable control than a deep-interceptor drain regardless of the nature of the waterlogging conditions.