USDA, NRCS, Watershed Science Institute WATERSHED ECOSYSTEM NUTRIENT DYNAMICS (WEND) Modeling Phosphorus (P) at a Watershed Scale: A Mass Balance Approach

USDA, NRCS, Watershed Science Institute WEND §A New Tool for Phosphorus (P) Management Using Off-the-Shelf Software §Used to Balance the Input and Output of P into, out of, and within a Watershed

USDA, NRCS, Watershed Science Institute Basic Watershed Concepts §Watersheds Store and Cycle P based on: u biological, physical, chemical mechanisms u management u land use development. §Phosphorus is stored in soils, sediments, biomass and wastes.

USDA, NRCS, Watershed Science Institute Basic Watershed Concepts §Phosphorus cycles and changes form due to biological, physical and chemical mechanisms. §Phosphorus cycles and changes location within and among land uses (sectors) within a watershed.

USDA, NRCS, Watershed Science Institute Sectors that Process Phosphorus §Agricultural u Cropland u Pasture u Animal Operations §Urban and Industrial §Woodland

USDA, NRCS, Watershed Science Institute P movement into, out of and within these sectors can be modeled using mass balance and dynamic simulation techniques.

USDA, NRCS, Watershed Science Institute ConceptualModel

Four Watersheds Modeled to Date

USDA, NRCS, Watershed Science Institute Models Developed for Different Land Uses and Animal Operations 1. The WEND-1 models the 275,000 ha (679,000 ac) Winooski River Watershed in Vermont, USA DairyDairy Silage Corn,Silage Corn, Hay, Pasture Hay, Pasture

USDA, NRCS, Watershed Science Institute Models Developed for Different Land Uses and Animal Operations 2. The WEND-IBW models the 77,000 ha (190,000 ac) Inland Bays Watershed in Delaware, USA PoultryPoultry Corn-Wheat- Soybean RotationCorn-Wheat- Soybean Rotation

USDA, NRCS, Watershed Science Institute Models Developed for Different Land Uses and Animal Operations 3. The WEND-LCW models the 23,800 ha (58,700 ac) Little Cobb River Watershed in Minnesota, USA SwineSwine Oats, Soybeans, & CornOats, Soybeans, & Corn

USDA, NRCS, Watershed Science Institute Models Developed for Different Land Uses and Animal Operations 4.The WEND-Eucha models the ha (231,700 ac) Lake Eucha Watershed in Arkansas and Oklahoma, USA PoultryPoultry PasturePasture

USDA, NRCS, Watershed Science Institute Characteristics of Watersheds Modeled

USDA, NRCS, Watershed Science Institute Characteristics of Watersheds Modeled

USDA, NRCS, Watershed Science Institute

Monitored Data vs. Modeled Estimates

USDA, NRCS, Watershed Science Institute Management Alternatives Simulated with WEND §Erosion Control §Manure Export

USDA, NRCS, Watershed Science Institute Management Alternatives Simulated with WEND §Increased Treatment of Point Sources §Animal Reduction

USDA, NRCS, Watershed Science Institute

Conclusions §WEND Models Are Valid For Evaluating P Management Scenarios For Watersheds §P Management Strategies Must Be Tailored To Fit Conditions in a Individual Watershed

USDA, NRCS, Watershed Science Institute Conclusions §P Sources Change Over Time §A Reduction in Non-Point Source P Export to a Drainage Net May Take Years

USDA, NRCS, Watershed Science Institute For Additional Information David Anderson NRCS Watershed Science Institute x46