On the simulation of areal average infiltration by simplified approaches

The possibility of synthesizing the effect of random variability of saturated hydraulic conductivity, Ks, on the production of overland flow at the hillslope scale is examined. Thus the areal average infiltration rate is approximated through the use of an equivalent spatially uniform saturated hydraulic conductivity, Kse. This quantity is determined by requiring conservation of the total volume of infiltrated water in a given rainfall event. Computation of Kse is performed using a coupled solution of the nonlinear kinematic wave for overland flow and the quasi-analytical model we developed earlier for local infiltration as a benchmark. It is shown that the use of Kse provided acceptable shapes of the hydrographs at the slope outlet. The Kse values are variable with rainfall pattern as well as with the parameters of the probability density function of Kg, however they should be easily expressed by a simple empirical relation.