Title

A discretized moisture content method for simulating the infiltration and redistribution of water in soil

Date of Completion

January 2008

Keywords

Engineering, Civil|Engineering, Environmental

Degree

Ph.D.

Abstract

A new one-dimensional infiltration and redistribution method has been developed as an alternative to the Richards' equation (RE) for coupled surface and subsurface models in homogeneous and layered soils. The proposed method discretizes soil water content into hypothetical hydraulically interacting bins. The entry and propagation of displacement fronts in each bin are simulated by means of explicit infiltration and drainage approximations based on capillary and gravitational driving forces. Wetting front advances within bins create water deficits that are satisfied by capillary-driven inter-bin flow. The method inherently provides numerical stability by precluding the need to directly estimate nonlinear spatial gradients through numerical schemes. To validate the method, it has been compared against RE solutions for theoretical, laboratory and field data in both well-drained and high water table conditions. The new method produces infiltration flux estimates with errors less than 10% compared to a widely used RE solution in tests on multiple soil textures with and without high water table conditions while providing unconditionally guaranteed conservation of mass. This new method represents another available method to modelers seeking to simulate infiltration and redistribution behavior in hydrologic applications where model scale and scope dictate the use of computationally less expensive methods.^