Evaluation and Validation of a Decision Support System for Selection and Placement of BMPs in the Mississippi Delta

Prevention and reduction of surface water pollution has been a matter of concern for decades, which has promoted the implementation of best management practices (BMPs) to ensure the protection of water resources. A considerable number of structural and non-structural BMPs have been developed to control hydrological processes and enhance pollutant load reduction at field and watershed scales. However, the selection of a specific BMP or the best combination of these practices and BMP placement are major challenges faced by decision makers. Recently, modeling tools have been presented as an effective alternative to support those challenges and to achieve cost-effectiveness in addressing environmental quality restoration and protection needs in different scenarios. USEPA has presented The System for Urban Stormwater Treatment and Analysis Integration (SUSTAIN) model to be used by watershed and stormwater professionals to develop, evaluate and select optimal BMPs combinations, at multiple watershed scales, and to achieve targeted water quality objectives based on cost and effectiveness. This tool incorporates algorithms from the Storm Water Management Model (SWMM), the Hydrologic Simulation Program FORTRAN (HSPF) model and other BMP modeling techniques. In order to evaluate and validate the application of the SUSTAIN model in an agricultural scenario, a case study is developed for a midsize drainage area (307 ha) located in the Mississippi Delta. The agricultural watershed includes a surface drainage ditch in which three low grade weirs have been installed and monitored for water level and pollutants concentrations since July 2010. The objective of this study is to assess the performance and capability of the SUSTAIN model in the context of a real agricultural scenario where BMPs are implemented. The study also attempts to determine the cost-effectiveness curve for the implementation of BMPs in the study area (considering the number of weirs installed as a variable) using total suspended sediments and total phosphorus as control targets.