Note that the data published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution. For the most recent data, purchase the 2008 Report from Island Press.

View Data on Total Phosphorus in Urban/Suburban Areas View Data on Ecosystem Comparison, Total Phosphorus in Streams, 1992-1998

What Is This Indicator, and Why Is It Important? This indicator reports the concentration of phosphorus in representative streams in urban areas. Specifically, the indicator reports the percentage of streams with average annual concentrations in one of four ranges, for streams draining watersheds that are primarily urban.

Phosphorus is an essential nutrient for all life forms and occurs naturally in soils and aquatic systems; phosphate is the most biologically active form of phosphorus. At high concentrations in freshwater systems, however, phosphorus can lead to algal blooms, which can decrease recreational and aesthetic values and help deplete oxygen needed by fish and other animals.

Sources of phosphorus in urban streams include effluent from sewage treatment plants, animal wastes, some detergents, and fertilizers used on lawns, gardens, golf courses, and agricultural fields.

What Do the Data Show? About two-thirds of stream sites in urban areas had concentrations of phosphorus that were at least 0.1 part per million (ppm), and about 10% of urban streams sites had concentrations of at least 0.5 ppm.

Streams in urban areas have similar average phosphorus concentrations to streams draining farmland watersheds.

Discussion The U.S. Environmental Protection Agency (EPA) has recommended 0.1 ppm as a goal for preventing excess algae growth in streams. In 2000, EPA took steps to facilitate development of regional criteria, but these regional criteria have not yet been adopted. There is no federal drinking water standard for phosphorus.