Development of a Best Management Practice (BMP) Placement Strategy at the Watershed Scale

Nonpoint source pollution control requires the implementation of best management practices (BMPs). There have been thousands of structural BMPs built in the United States since the stormwater regulations were enacted in the late 1980's and early 1990's. The number will keep increasing in light of that the NPDES Phase II regulations are to be implemented within a few years. Most structural BMPs have been installed at the local level, or "on-site", and not at the regional or watershed level in a comprehensive manner. In recent years, the USEPA is promoting the "watershed approach" in controlling pollution from various sources in a watershed. One important aspect of the watershed strategy should be the optimal placement of the BMPs so that the combined effects of the BMPs will provide the most cost-effective way of treating stormwater. In this paper, a methodology is developed to assist in the determination of BMPs placement strategies at the watershed scale. The AGricultural Non-Point Source Pollution Model 2001 developed by USDA, is used for the BMP placement analysis. The relative effectiveness of BMP at three different spatial placement levels, i.e. on-site, sub-regional and regional levels, is compared. BMP simulation models are used in connection with AGNPS 2001 to evaluate BMP performance in the context of an entire watershed. Based on the model simulation results, a BMP placement optimization approach is developed to determine a most cost-effective BMP placement strategy at the watershed scale. A hypothetical case study is described in the paper to illustrate the methodology.