Simplified Model for Simulating Basin-Scale Surface Runoff Hydrographs

A simplified model for estimating the hydrologic response to rainfall events at basin scale is developed in this study. It involves an abstraction of the real basin geometry based on networks of planes and channels and three semianalytical components that give the expected areal-average infiltration rate at field scale, the surface runoff hydrograph as lateral inflow into the channel network, and the water flow routing through the channel network. The model was tested by comparison with Monte Carlo simulations that relied on a detailed representation of spatial variation of excess rainfall and numerical solutions of water routing through planes and channels. The peak flow and the shape of the hydrographs were generally well reproduced. The results were less accurate for cases involving low volumes of effective rainfall, but these are of less importance in hydrologic practice. In spite of the complexity of the processes represented, such as the spatial heterogeneity of soil saturated hydraulic conductivity and rainfall rate as random variables over each subwatershed, the model requires a low computational effort that makes it suitable for application at all levels of spatial discretization.