Watershed Modeling

RESPEC’s engineers and scientists specialize in applying physics, chemistry, aquatic biology, geology, ecology, and mathematical modeling, which allows us to evaluate watershed conditions and drivers and propose effective management alternatives. Our staff are among the principal scientists and engineers who participated in the original development of the U.S. Environmental Protection Agency’s (EPA) Hydrological Simulation Program – FORTRAN (HSPF). Since 1981, our staff have performed all the HSPF code maintenance for the EPA, and our responsibility continues today. In this capacity, we are widely regarded as the premier experts in all operational, software, and application aspects of the model. Our staff have been the principal authors of all HSPF User’s Manual and HSPF Application Guide versions. In addition, RESPEC staff have developed an array of customized software in response to client needs. We have served as the primary developers and maintainers of EPA’s Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) for over 20 years. To support the San Antonio River Authority’s (SARA) holistic watershed master planning, RESPEC staff developed a suite of innovative water quality modeling tools to allow quantitative water quality master planning and best management practice (BMP)/low-impact development (LID) prioritization in SARA watersheds. The SARA Load Reduction Tool automatically determines the load reduction needed for each subbasin and constituent to meet user-specified water quality concentrations. The SARA BMP Processor compiles individual BMP/LID unit cost and effectiveness information to assess potential incentives for implementing BMPs/LIDs. The SARA Enhanced BMP Tool determines the optimal combinations that would minimize BMP/LID costs while achieving the needed load reduction.

RESPEC has been involved in watershed modeling for over 40 years. Our most recent projects have included modeling sediment, nutrients, temperature, and dissolved oxygen in the Pawcatuck River Watershed in Rhode Island and Connecticut, as well as a suite of models covering the entire state of Connecticut. Additionally, RESPEC is currently modeling Octoraro Creek in the Chesapeake Bay drainage in southern Pennsylvania and northern Maryland. RESPEC modeled the Cape Fear River Basin in 2014. For the Cape Fear model, we used the Soil and Water Assessment Tool (SWAT). Over the past 5 years, RESPEC has developed watershed model applications for 57 of the 77 Hydrologic Unit Code 8 (HUC8) watersheds in the state of Minnesota.

RESPEC’s internally developed Scenario Application Manager (SAM) is an open-source tool that puts the power of HSPF applications into practitioners’ (i.e., non-watershed-modeling experts) hands. HSPF-SAM is a user-friendly, comprehensive decision support tool for planning and implementing targeted actions to restore or protect water quality. The framework of the HSPF-SAM includes a Geographic Information System (GIS) for BMP site selection; a BMP database with pollutant removal efficiencies and associated costs; and scenario analysis, optimization, and reporting capabilities. It allows clients who have invested in an HSPF to understand watershed conditions and identify priority areas and BMPs that will provide the greatest water quality benefits for each dollar invested.

RESPEC has been doing in-person HSPF training for as long as we have been using the HSPF model (40 years). In recent years we have also provided virtual training and developed material for SAM training sessions that can be used in person or virtually. Our staff are seasoned trainers and have given these training sessions for many HSPF and HSPF-SAM users in Minnesota and Connecticut. Over time, past clients have desired extensions of their HSPF model applications and SAM tools to represent the most recent possible time periods for Total Maximum Daily Load (TMDL) and implementation planning studies.

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