PONDED INFILTRATION INTO SOILS BOUNDED BY A WATER-TABLE

A simple model of ponded infiltration into homogenous soils bounded by , and at steady state equilibrium with, a water table is presented. Th e model parameterizes the wetting front profile as a tension-saturated zone above a zone in which the moisture content decreases linearly wi th depth. Application of the model requires numerical evaluation of an integral relating the time since the onset of pending to the infiltra tion rate or wetting front position. Wetting fronts predicted by the s implified model compare favorably with laboratory measurements of Vach aud and Thony (1971) and, for a wide range of soil types, with those p redicted by finite-element integration of the governing flow equations . The presence of a shallow water table causes the infiltration rate t o decrease faster than it would under semi-infinite conditions with un iform initial moisture content. Infiltration equations for soils bound ed by water table may be used in distributed hydrologic models and oth er applications where the shallow position of the water table signific antly affects the partitioning of precipitation forcing during storms.