Numerical study of the effects of layers on unsaturated-saturated two-dimensional flow

Unsaturated-saturated flow due to infiltration and/or redistribution in heterogeneous soils is a complex phenomenon. Numerical problems are considered and the effects of size and location of continuous or discontinuous layers of low permeability on cumulative infiltration, infiltration rate, moisture content profile, and water-table response under spatially-discrete ponding conditions are studied at an experimental scale using a two-dimensional unsaturated-saturated model based on the Richards equation. The results illustrate complex response but indicate that the spatial distribution and soil characteristics of layer(s) are dominant factors. Fine layers significantly reduce surface infiltration, although the reduction of infiltration is not sensitive to their thickness. Two-dimensional effects are important; perched water tables above fine layers spread laterally and may result in air entrapment.