Phosphorus is a common element in agricultural fertilizers, manure, and organic wastes in sewage and industrial discharges. Excess phosphorus in lakes, rivers, and streams causes algae to grow. Algae-covered water is less attractive for fishing and swimming — highly valued pastimes in Minnesota and uses that are protected under the federal Clean Water Act — and degrades conditions necessary for fish, bugs, wildlife, and plants to thrive. In addition, phosphorus can fuel toxic blue-green algal blooms, which are harmful to people and pets

Minnesota has studied the levels and sources of phosphorus in lakes, wetlands, rivers and streams. To protect waters in the state and flowing beyond its borders, Minnesota is also implementing a Nutrient Reduction Strategy. For more information, contact Dennis Wasley at the MPCA, 651-757-2809, toll-free at 1-800-657-3864, or by e-mail at

Atmospheric deposition: 2007 update

PDF icon Detailed Assessment of Phosphorus Sources to Minnesota Watersheds - Atmospheric Deposition: 2007 Update

Addresses atmospheric deposition as a source of phosphorus to Minnesota watersheds. This discussion builds upon the analysis conducted in 2003 and is based on a review of the available literature, consideration of monitoring data and other available support data, and includes the results of phosphorus-loading computations for each of Minnesota’s ten major watershed basins.

Detailed Assessment of Phosphorus Sources to Minnesota Watersheds (2004)

In 2003, concerns about the phosphorus content of automatic dishwashing detergents prompted the passage of legislation requiring a comprehensive study of all of the sources and amounts of phosphorus entering publicly-owned treatment works and, ultimately, Minnesota surface waters. The assessment, funded by the Legislative Commission on Minnesota Resources and conducted for the MPCA by a consulting firm, is the first scientific study of just how much phosphorus enters Minnesota's lakes, wetlands, rivers and streams, and where it comes from in each of the state's 10 major watersheds.

Findings. The study found that statewide, automatic dishwashing detergents contribute about three percent of the total phosphorus load to state waters. Under normal water flow conditions, roughly two-thirds of the total load comes from nonpoint sources: runoff from cropland and pasture supplying most of the load, with lesser amounts coming from streambank erosion, urban runoff and atmospheric deposition. Approximately 31 percent of the phosphorus load comes from point sources such as wastewater treatment facilities and industrial treatment facilities.

Legislative Report: Detailed Assessment of Phosphorus Sources to Minnesota Watersheds