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 dennis.wasley@state.mn.us.
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
Cover Letter to Legislature
Cover Page, Acknowledgements and Table of Contents (file size=1.4 MB)
Executive Summary (file size=4.9 MB)
Section 1: Introduction (file size=1.1 MB)
Section 2: Methods (file size=584 KB)
- Section 3: Results and Discussion (this section is broken into sections due to large file sizes)
Section 3.1: Basin Hydrology (file size=5.1 MB)
Section 3.2: Estimated Basin Total Phosphorus Amounts Contributed to POTWs and Surface Waters (by Source) (file size=781 KB)
Section 3.3: Summary of Phosphorus Loadings by Basin (file size=2.2 MB)
Section 3.4: Phosphorus Sources and Estimated Amounts Contributed to Surface Waters (by Basin, Total and Bioavailable) (file size=3.0 MB)
Section 3.5: Comparison of Total Phosphorus Loadings from All Sources with Monitored Loadings in Minnesota and Upper Mississippi River Basins (file size=56 KB)
Section 3.6: Effluent Total Phosphorus Reduction Efforts by Wastewater Treatment Plants (file size=102 KB)
Section 4: Recommendations (file size=176 KB)
Section 5: Overall Conclusions (file size=60 KB)
References (file size=238 KB)
Appendices Cover Page (file size=1.3 MB)
Appendix A: Basin Hydrology Technical Memorandum (file size=6.1 MB)
Appendix B: Point Sources Technical Memorandum (file size=2.2 MB)
Appendix to Appendix B (file size=327 KB)
Appendix C: Cropland and Pasture Runoff Technical Paper (file size=376 KB)
Appendix C Figures 1-14 (file size = 6.3 MB)
Appendix C Figures 15-25 (file size = 6.8 MB)
Appendix D: Feedlot Runoff Technical Memorandum (file size=574 KB)
Appendix E: Atmospheric Deposition Technical Memorandum(file size=1.7 MB)
Appendix F: Deicing Agents Technical Memorandum (file size=1.2 MB)
Appendix G: Streambank Erosion Technical Memorandum (file size=860 KB)
Appendix H: Individual Sewage Treatment Systems (ISTS)/Unsewered Communities Technical Memorandum(file size=575 KB)
Appendix I: Non-Agricultural Rural Runoff Technical Memorandum(file size=4.3 MB)
Appendix J: Urban Runoff Technical Memorandum(file size=1.2 MB)
Appendix K: Bioavailable Phosphorus Technical Memorandum(file size=480 KB)
Appendix L: Effluent Total Phosphorus Reduction Efforts by WWTPs Technical Memorandum (file size=198 KB)