National Water-Quality Assessment (NAWQA) Program
1 Reported share for the Great Lakes is from confined livestock waste only; reported share for California estuaries is from unconfined livestock waste only (see Ruddy and others, 2006, for definitions).
2 Reported share for the Great Lakes and the Gulf of Mexico estuaries also includes nitrogen fixation by agricultural crops; reported share for California estuaries also includes waste from confined livestock.
3 Share is not estimated for the Great Lakes; reported share for the Pacific Northwest estuaries also includes estimated share from septic waste.
4 Forested-land share is reported separately only for Pacific Northwest and California estuaries; for other regions the share is assumed to be included in the atmospheric deposition term.
5 Reported for the Pacific Northwest estuaries only, consists primarily of load delivered from Canada with a small amount from springs and return flows from power plants within the United States.
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Access maps of watershed nutrient contributions to the Nation’s Estuaries.