A Simulation Model for Predicting Infiltration into Cracked Clay Soil

Infiltration into dry cracked clay soil was simulated by combining two existing physical simulation models for vertical and horizontal infiltration, using boundary conditions for horizontal infiltration that were defined by morphological data. Vertical flow into the cracks occurred when the application rate exceeded the calculated vertical infiltration rate of peds between cracks. Calculated horizontal infiltration from the cracks into adjacent dry peds was limited because it had to occur from a few small vertical bands along which the water moved. The contact area ( S ) of all bands had been determined in situ in 0.5‐m 2 plots per 10‐cm depth interval using morphological staining techniques. S was a function of the applied flow regime. “Short‐circuiting,” which was defined as preferential movement of free water along large pores through unsaturated soil, was predicted well by the model. Short‐circuiting increased when the initial moisture content of the soil was higher.