Unconfined Aquifer Seepage by Capillary Flow Theory

A numerical scheme is presented to analyze a two-dimensional unconfined aquifer of rectangular cross-section to determine the fall of the water table, the water content and the rate of outflow into an adjoining water body which fully penetrates the aquifer. The capillary or unsaturated flow above the water table is considered through the use of Richards' equation. It was found that the problem can be solved by an alternating explicit-implicit finite difference scheme. It has the advantage of being efficient and of being suitable even when the fully saturated flow zone is very small. The unknown position of the seepage surface and the unknown boundary between the saturated and the unsaturated zone constitute a very critical aspect of the calculations.