A desk top model has been developed for "user-friendly" application in personal computers to simulate watershed response to a rainfall event in terms of runoff generation and to estimate nonpoint source pollutant loadings associated with the storm event. The algorithms utilize the SCS TR - 55 method for calculating runoff hydrographs for a single storm event. A methodology has been adapted to generate pollutographs which combines the SCS Type II rainfall distribution with the standard pollutant washoff equations. In addition, this model allows for the design, evaluation, and cost effectiveness analysis of various best management practice (BMP) measures as tools to manage stormwater quantity and quality.