Modeling local infiltration for a two-layered soil under complex rainfall patterns

A general model for local infiltration-redistribution-reinfiltration in a two-layered soil profile is proposed as an extension and generalization of a formulation we developed earlier for infiltration and redistribution in crusted soils. It is of analytical/conceptual type and involves a Runge-Kutta-Verner numerical solution of a system of two ordinary differential equations. Given the basic hydraulic properties of soils, there are practically no parameters to estimate by calibration. The wetting profile during infiltration is represented by a single similarity curve, while in the reinfiltration stage, which occurs for rewetting after a period of redistribution, the profile of soil water content in each horizontal layer may be composed of two similarity profiles which evolve in time. The model is tested by comparison with numerical solution of Richards’ equation, carried out for a variety of synthetic experiments upon the combination of three soil types of contrasting hydraulic characteristics. It simulates particularly well the entire cycle infiltration-redistribution-reinfiltration. In all cases, where either layer may be less permeable, the water content at the surface and the interface as well as the infiltration rates are very accurately estimated. The usefulness of compound profiles of water content in the reinfiltration stage is also shown by comparison with the simple approach, which relies on a single similarity curve.