Phosphorus is an essential plant and animal nutrient that can impair surface water quality when present in excess. Phosphorus occurs naturally and is commonly found in fertilizers, manure, detergents, municipal and domestic sewage, and industrial waste. Phosphorus must be carefully managed to minimize the impact on surface water quality.

Although phosphorus is essential for all living things, excess in surface water can degrade water quality and cause a variety of problems. Both agricultural and nonagricultural sources contribute phosphorus to lakes, rivers and streams. All sources must be managed to maintain water quality, however, more than one approach is necessary.