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Estimating Nitrogen Loads, BMPs, and Target Loads Exceedance Risks
Citation:
Yang, G., Elly Best, A. Teklitz, T. Whiteaker, L. Yeghiazarian, AND D. Maidment. Estimating Nitrogen Loads, BMPs, and Target Loads Exceedance Risks. Presented at American Water Resources Association (AWRA) 2013 Spring Specialty Conference, St. Louis, MO, March 25 - 27, 2013.
Impact/Purpose:
To inform the public.
Description:
The Wabash River (WR) watershed, IN, drains two-thirds of the state’s 92 counties and has primarily agricultural land use. The nutrient and sediment loads of the WR significantly increase loads of the Ohio River ultimately polluting the Gulf of Mexico. The objective of this study was to increase the understanding of spatial and temporal patterns of the non-point and point source discharges of nutrients in the WR watershed and use this information as a basis for the planning of best management practices (BMPs) limiting nutrient loads downstream. First a hybrid statistical and process-based modeling approach was developed within the ArcGIS environment to estimate nutrient loads and transport in surface waters of watersheds. This approach was expanded with a capability to evaluate the probability of nutrient loads to exceed target loads using probabilistic risk assessment, and produce spatial risk maps visualizing exceedance categories. The combined modeling approach was used to explore BMP scenarios within the Tippecanoe River watershed, a northern part of the WR watershed. Scenarios and acreages for implementation were based on recent Conservation Effects Assessment Project (CEAP) outcomes and the IN Conservation Reserve Enhancement Program (CREP). Estimated decreases in annual total nitrogen (TN) loads at the HUC-8 watershed pour point due to BMP implementation was up to 4.2%, with buffer strips producing the largest decrease. The accompanying risk maps illustrated the locations with the greatest risk to exceed the target TN load in this watershed. This combined approach can be used to estimate TN loads and transport in watersheds at various spatial scales, and explore the potential of BMPs to diminish nutrient loads in support of sustainable integrated watershed management planning. A follow-up study will address phosphorus. Oral presentation at ‘Agricultural Hydrology and Water Quality II’, American Water Resources Association (AWRA) 2013 Spring Specialty Conference, March 25-27, 2013, St. Louis, Missouri.
