A Management strategy for utilization of water resources in the planned community of the Woodlands, near Houston, Texas, was developed by modification and application of the EPA Storm Water Management Model (SWMM). The capacity of the SWMM to model urban runoff quantity has been improved to include the 'natural' drainage concepts of the Woodlands and the infiltration computation model in the SWMM is now capable of operating with a rainfall record which includes periods of zero rainfall. Three new subroutines generate normalized area-discharge curves for natural sections, model baseflow conditions, and model the operation of porous pavements, respectively. Verification of the SWMM with regard to suspended solids and BOD5 was attempted and modifications to predict COD, Kjeldahl nitrogen, nitrates and phosphates were performed. This innovative water quality modeling scheme has proved very successful in predicting future effects of urbanization.