Prediction of Water Table Mound Development and Aquifer Recharge from an Infiltrating Area

Abstract

Typically intermittent streams (wadis) and zones of infiltration during and shortly after a rain or a flood are not in permanent hydraulic connection with the underlying water-table aquifer. Due to the frequent presence of a clogged layer the water flow below the infiltration zone is often unsaturated. Recharge occurs only after the unsaturated wetting front reaches the water-table. On the other hand, long after infiltration has ceased at the soil surface, recharge continues from the unsaturated storage which has accumulated above the water table during the infiltration phase. This distinct phase of recharge after infiltration has stopped is called the drainage phase. The problem is two or three-dimensional in nature. To simplify the predictive tool and make it very practical, the multi-dimensional character of the flow problem is rendered, approximately but effectively, by a special technique that consists of matching two unidimensional flows, a vertical and a horizontal one. Practical examples illustrate the influence of the parameters on the water table level below the infiltrating area and on the lateral recharge rate into the part of the aquifer which is not overlain by the river or infiltration basin bed. Comparison with field observations shows the technique to be accurate, inexpensive and easy to apply