MODELING PREFERENTIAL FLOW OF WATER IN SOILS - A 2-PHASE APPROACH FOR FIELD CONDITIONS

A conceptual two-phase model for preferential flow of water through field soils is proposed. The first phase represents times of redistribution and low infiltration, which does not generate preferential flow. Times of heavy infiltration, inducing preferential flow, are handled by the second phase. The Richards equation is applied as the governing flow equation for both phases and preferential flow is allowed for by increasing the hydraulic conductivity of the soil during the second phase. The parameters of the model were estimated by use of different techniques, including a transient field experiment and the subsequent solution of the inverse problem. The model was tested and a reasonably good agreement between simulated and experimental data was obtained. When long-term. effects of preferential flow, rather than an event-specific representation of the involved processes are in focus, the presented model seems to be an adequate approach. More specific parameter estimation techniques are a possibility to further improve the applicability of the model.