Formation and calculation of watershed runoff yield

By the Horton and Dunne runoff generation theories,this paper discusses the mechanism of watershed runoff yield,develops concepts of the runoff formation at the natural storage and the runoff formation in excess of infiltration,and analyzes the influencing factors of watershed runoff yield and the contributing area change characteristics.It's emphasized that these two generation mechanisms of good universality in nature are the important basis in building the runoff yield module of watershed hydrology models.Only the influence of spatial heterogeneity of underlying surface factors on watershed runoff yield under the situation of the spatial homogeneity of rainfall can be considered with the method of watershed storage capacity curve and infiltration capacity area distribution curve.With the development of rainfall measurement by radar and satellite remote sensing technique and the application of GIS technique,however,grid method is expected more direct and reasonable in considering the influence of spatial heterogeneity of rainfall and underlying surface factors on the watershed runoff yield.