Two‐dimensional soil moisture flow in a sloping rectangular region: Experimental and numerical studies

Results from experiments with a 3.66 by 0.58 by 0.108 m flume filled with sand are used to study the two‐dimensional flow of soil moisture under the condition of rainfall infiltration. The experimental results are compared to results obtained by a numerical solution (via a finite element‐finite difference transformation) of the two‐dimensional Richards equation. The results are presented in the form of flow field conditions (hydraulic head distribution and position of the phreatic surface) and the rising limb of the runoff hydrograph. The experimental and the numerical results are in satisfactory agreement when the effect of capillary hysteresis is incorporated into the numerical solution. When capillary hysteresis is ignored, the numerically simulated hydrograph lags far behind the experimentally derived hydrograph.