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The Chesapeake Bay estuary is a major estuary that is under great stress. The watershed has a land area of approximately 180,000 km2, and a total water surface area of 9,890 km2. Agriculture is the largest contributor of nonpoint source pollution. nutrient control actions had been taken through 2008 to reduce the amount of nitrogen entering the bay annually to about 128.6 million kg of nitrogen and 7.4 million kg of phosphorus. To achieve water quality standards in the Bay, the Chesapeake Bay model estimates suggest that nitrogen needs to be reduced to 90.8 million kg a year and phosphorus to about 6.8 million kg. Virginia, Delaware, Maryland and Pennsylvania all have nutrient management regulations. The nutrient management regulations appear to have an effect of reducing the nutrient loads to the Bay. Agriculture has made considerable progress in reducing nitrogen and phosphorus loads from 1985 baseline loads. More progress has probably been made with reducing loads from cropland then loads from animal agriculture. Pennsylvania and Virginia regulations apply to manure and animal agriculture while Delaware and Maryland regulations apply to all sources of nutrients.