A unified model for infiltration and redistribution during complex rainfall patterns

A relatively simple conceptual model for infiltration during complex rainfall sequences is presented. It is a reformulation of an analytically derived model developed earlier by Smith et al. (1993) [Water Resour. Res., 29(1): 133-144] and Corradini et al. (1994) [Water Resour. Res., 30(10): 2777-2784] in a more homogeneous version suitable for hydrologic applications. The model relies on a single ordinary differential equation through which successive cycles of infiltration-redistribution can be described. The wetting profile, theta(z), is described by a single similarity curve which is stretched in both z and a dimensions in accordance with the curve area, I, representing infiltrated water. The actual profile of soil water content after rewetting may be compound, composed two parts, each part represented by a similarity profile shape which evolves in time. The model is calibrated using a silty loam soil and is then tested on a variety of soils, from fine-textured to sandy loam soil types, by comparison with a numerical solution of the Richards equation. Like the earlier formulation, the model simulates infiltration rate particularly well, and the greater simplicity of this model sacrifices very little accuracy of the earlier, more complex model. (C) 1997 Elsevier Science B.V.