Evaluation of BMP Effectiveness in Southern California Using an HSPF Water Quality Model

As the Clean Water Act Section 303(d) and Total Maximum Daily Load (TMDL) programs progress, dischargers are faced with the realities of implementing effective pollutant control strategies. The goal of this project was to evaluate the effectiveness of various best management practice (BMP) strategies to help improve water quality and comply with water quality objectives in two watersheds in Southern California. The team developed water quality models that provide an evaluation of the effectiveness of the BMPs at reducing pollutant loads. Several BMP scenarios were evaluated using the watershed models to help identify the most beneficial strategy and the best locations for the BMPs.Numerous challenges were encountered during the development of the models. These include lack of water quality monitoring data, sparse rainfall events, and missing information on the hydrologic characteristics of the region. These required that an adaptive approach be used for the model. The recommendations of this study include strategies to answer these challenges.The model allowed the project team to evaluate the improvements to receiving water quality in terms of each of the pollutants of concern and against the total costs for each scenario. The technical paper includes a discussion of the methodology used, the challenges confronted, the lessons learned, and the conclusions of the project.