An Alabama BMP database for evaluating water quality impacts of alternative management practices

Best management practices (BMPs) are often used to control nonpoint source (NPS) pollutants from agricultural, forested, and urban watersheds. NPS models are used to estimate pollutant loads, devise NPS abatement plans, and develop and implement Total Maximum Daily Load (TMDL) plans. Accuracy of NPS model prediction depends on, among other things, the accuracy of input data, which includes accurate description of BMPs. Although detailed BMP description can be obtained by using extension manuals and talking to experts, a comprehensive BMP database for use by watershed modelers and water resource managers are usually unavailable. In the absence of regionally appropriate BMP database, simplified assumptions arc, often used. This practice can introduce input data uncertainty in models, which can lead to poor model predictability, and mistrust in models. To alleviate this problem, a comprehensive database of commonly used agricultural and forestry BMPs in Alabama was developed. Using this database, various NPS pollution abatement measures can be evaluated using the SWAT (Soil and Water Assessment Tool) or other distributed parameter, continuous simulation NPS model. Specific objectives were: (1) to develop a database of commonly used BMPs in agriculture and forestry for the State of Alabama and (2) to create an ArcView (R) 3.X GIS (Geographic Information System) extension to load the database into the SWAT model. The complete database containing hundreds of BMPs and supporting documents are available at http://www.eng.auburn.edu/ users/srivapu. The database provides environmental professionals with detailed information on management of agricultural and forested lands. This type of detailed information is currently unavailable in Alabama and many other states. Using the BMP database with the SWAT model, environmental professionals will be able to evaluate the site-specific effectiveness of BMPs and conduct more accurate assessments of NPS pollutant loads, TMDLs, pollutant trading, and BMP implementation plans. Overall, this will allow environmental professionals to make more confident BMP recommendations and manage watersheds more effectively. Additionally, the methodology presented can be used by other states to develop region-specific BMP databases.