Effective Hydraulic Parameters for Sloping Heterogeneous Soil Formations.

Landscape sloping is an important factor in many hydrological processes. Soils are commonly layered under field conditions. The Green-Ampt model is a simplified but a widely used representation of infiltration process. In this study we consider these three aspects in examining effective soil hydraulic parameters in sloping layered soil formations in combination with the Green-Ampt model. In particular, we investigate the effects of layered heterogeneity on ensemble infiltration behavior and effective Green-Ampt parameters in a sloping landscape. We also address the impact of layered hydraulic property uncertainty and correlation on upscaled Green-Ampt parameters. Various averaging schemes of Green-Ampt parameters are compared with effective parameters calculated by conceptualizing the sloping layered heterogeneous soil formation as an equivalent homogeneous medium that will infiltrate approximately same amount of flux of the heterogeneous soil. We examine how landscape slope affects upscaling schemes of Green-Ampt model in rainfall-runoff processes. The impact of layer structure and hydraulic parameter correlation on the effective Green-Ampt parameters, as well as the accuracy and uncertainty of the averaging schemes are also investigated and discussed.