A watershed of any configuration, topography, spatial distribution of cover and soil, and channel characteristics is described as a nonhomogeneous finite-element surface grid. Time-varying precipitation is applied to the watershed and runoff is hydraulically routed over the surface in discrete time increments. Infiltration is abstracted by a variable rate model derived from SCS curve numbers. Precipitation infiltrates, stands, and/or runs off each quadrant in accordance with that quadrant’s slope and hydrologic characteristics. Overland flow is routed to channels, and channel flow is then routed to the basin’s point of discharge. The grid definition of the watershed surface makes the model appropriate for watersheds not adequately modeled by conventional, nondistributed hydrologic means. The model does not require that unit hydrographs or times-of-concentration be estimated.