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Development of the Conceptual Design for a Comprehensive WQ Model of the St. Louis Bay Estuary and Watershed, #MX974070

Project Title: Development of the Conceptual Design for a Comprehensive WQ Model of the St. Louis Bay Estuary and Watershed, Project MX974070

Purpose of this project: To develop a conceptual design and framework for extending the capabilities of the fecal coliform water quality model to an ability to estimate a more comprehensive set of water quality parameters including dissolved oxygen and nutrients. The nutrient model of the St. Louis Bay estuary loosely couples watershed, hydrodynamic and water quality models. The Better Assessment Science Integrating Point and Nonpoint Sources (BASINS 3.0) and the windows implementation of the Hydrologic Simulatio Program-Fortran (WinHSPF) computer programs were applied to develop a watershed scale model of the hydrologic and nutrient processes within the study area. The developed watershed model simulated nonpoint source flow and nutrient loadings for all sub-watersheds, routed flow and water quality, and major point source discharges in the St. Louis Bay watershed. Initial calibration is illustrated and representative simulations are presented.

The performance of the developed watershed model was varied. The simulated dissolved oxygen concentration closely matched instream measurements from the Wolf River except during periods of extremely low flow. Modeled BOD also closely matched instream data collected during several rain events. However, the simulated nitrogen and phosphorus concentrations did not reflect measured instream nitrogen concentrations, with simulated values on to two orders of magnitude higher than observed levels.

The products from the project included:

  1. A calibrated and verified model of the Bay of St. Louis;
  2. An assessment of model sensitivity and project report summarizing tasks and accomplishments (1document);
  3. User guide

Gulf of Mexico Program Office
Mail Code: EPA/GMPO
Stennis Space Center, MS 39529-6000
228-688-3726
FAX: 228-688-2709


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