Infiltration over Heterogenous Watershed: Influence of Rain Excess

Abstract

Once the soil surface reaches saturation, rain excess is generated. This rain excess may run over and infiltrate in other areas of the watershed. In this study, we consider three scenarios of distributing rain excess/run-on to examine how it affects infiltration over a watershed. For these scenarios, we introduce simple solutions that allow the users to (1) estimate the ponded area-fraction of the watershed, and (2) determine the area-averaged infiltration. The solutions are practical because they require trivial computations. The solutions of ponding time and area-averaged infiltration account for the influence of initial water content and contain parameters with precise physical meaning. We find that area-averaged infiltration depends strongly on the distribution of rain excess at the surface. Thus we question the use of many stochastic area-averaged infiltration models that ignore the influence of rain excess.