National Water-Quality Assessment (NAWQA) Program
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Model findings show that 22 watersheds are reliably placed in the top 150 category for total phosphorus delivered to the Gulf of Mexico with 75 percent certainty. A total of 573 watersheds for total phosphorus yields are reliably placed outside of the top 150 category with 75 percent certainty. Although probabilistic ranking of watershed nutrient yields can be used as one tool to identify watersheds with the highest nutrient yields delivered to the Gulf of Mexico, this large-scale approach may not address nutrient management needs to protect streams and reservoirs at a local scale.