A mathematical model to stimulate overland and channel flow using the finite element technique was adapted and applied to a small semiarid rangeland watershed (2035 acres) in the USDA Walnut Gulch experimental watershed in the southwestern United States. The Holtan equation was used to estimate precipitation excess, and with the precipitation excess as input, the finite-element technique was used to route overland and channel flow. The program was structured with sufficient flexibility so that the effect of land use changes, either gradual or sudden, on the runoff hydrograph could be estimated. Abstraction losses in the stream channel are accounted for. The simulation model predictions are compared with field data for several storms, and the comparisons are satisfactory; however, improvements could be made with additional data on antecedent moisture content and better estimates of abstraction losses. Based on these comparisons, it is felt that the model can be used to estimate runoff hydrographs from ungaged watersheds in semiarid regions.