HSPF Toolkit: A Tool for Stormwater Management at the Watershed Scale

The Hydrological Simulation Program – FORTRAN (HSPF) is a semi-distributed-parameter conceptual watershed model that simulates hydrology and water quality constituents at various user-defined temporal (1-min to 1-day simulation time steps) and spatial resolutions (one square meter to hundreds of thousands of square kilometers). HSPF subdivides watershed landscape into pervious, impervious, and surface water segments, each represented by a different application module. The pervious land segment is simulated within the PERLND, the impervious land segment within the IMPLND, and the surface water reaches within the RCHRES application modules, respectively. Its representation of landscapes in this manner makes HSPF highly suitable for modeling streamflow and water quality for watersheds with mixed land uses. HSPF is routinely used to develop source control plans to achieve pollutant total maximum daily load (TMDL) levels in impaired water bodies; as such, it is the core watershed model in the US EPA BASINS 4.0 (Better Assessment Science for Integrating point and Nonpoint Sources) modeling framework. HSPF's limitations include an inability to explicitly represent storm sewer networks and urban best management practices (BMPs). The toolkit presented herein is designed to address these limitations.