A statistically-based runoff-yield model

This paper describes a statistical-based rainfall-runoff model considering spatial variation of rainfall and other factors that control the runoff-yield process. Both infiltration excess and saturation excess runoff-yield mechanisms are coupled in this model. The spatial variation of a rainfall event is described by introducing a probability density function (pdf) constructed by combining a simple linear function with a negative exponential function. Meanwhile, the soil infiltration capacity over a basin is simulated by a parabolic type pdf. According to the joint probability distribution of rainfall and soil infiltration capacity, the probability distribution of the surface runoff can be derived, a quasi-analytical solution for surface runoff is obtained, and furthermore the surface runoff and soil infiltration are computed by adopting the infiltration excess mechanism. Part of the infiltration supplements the soil moisture, and the rest recharges to subsurface and groundwater flow through using a water storage capacity curve. The total runoff is composed of infiltration excess and saturation excess runoff. As an example, the model was applied to Lushi basin, a sub-basin at the middle reach of the Yellow River. Results were compared with those obtained by TOPMODEL; it is shown that the model presented in this study is applicable to such a basin with semi-humid or semi-arid hydrological characteristics. Copyright © 2008 IAHS Press.