An unlined irrigation canal has been aligned parallel to a river, as shown (next page). This cross-section continues for 5.25 miles (length of irrigation canal). The predominant soils are generally clayey soils with extremely low permeability, but the geotechnical engineer realized that a 6 in thick sand seam is present as shown (thickness perpendicular to the flow). The sand has a hydraulic conductivity of 8.2 x 10 cm/sec. (A) Compute the water loss from the canal to the river due to seepage through this sand layer and express your answer in acre-foot per month. Note: One acre-foot is the amount of water that would cover one acre of ground to a depth of one foot, and thus equals 43,560 ft.

In hydrology, when water flows down in a pore or crack of unsaturated soil due to gravity, the deep layer of soil is called seepage. It is the slow movement of water in the soil layer. Seepage is mainly found near hydraulic structures and is responsible …