Unlike point sources that usually come from pipes, nonpoint sources (NPS) of phosphorus stem from surface runoff or snowmelt. The activities occurring on the land, or the "land use", has a direct influence on the quantity and quality of the runoff. Nonpoint sources contribute about 90% of the total phosphorus load to Lake Champlain. A 2007 report for the LCBP estimated the contribution of NPS phosphorus from major land use types:

• Agricultural Land (38% of NPS phosphorus)
• Urban and Other Developed Land (46% of NPS phosphorus)
• Forest Land (15% of NPS phosphorus)

The Phosphorus Loading by Land Use Map [242 KB] illustrates the percentages of NPS phosphorus loads to Lake Champlain from agricultural land, forested land, and developed land for each of the Lake's sub-watersheds, based on 2001 land use data. As land uses vary throughout the Basin, NPS phosphorus loads are also different. The full report is available on the LCBP website publications page.

Urbanization has many negative impacts, including pollution from urban activities, increases in stormwater runoff, and physical changes to river systems and other natural filters such as wetlands. On average, urban and suburban land contributes up to four times the phosphorus per unit area than either agricultural or forested land. Although it only constitutes 5% of the land use, it is estimated to contribute about 46% of the phosphorus! Development increases the amount of impervious area (e.g. roof tops and pavement) in a watershed, which interferes with the natural filtering ability of soils. The quantity of runoff also increases because the soils can no longer absorb and store rain and snowmelt. Suburban and rural residential areas, commercial developments, industries, and roads all contribute phosphorus. Activities such as washing cars on roads and driveways, not cleaning up pet waste, over-fertilizing lawns and gardens, can all contribute to nonpoint source phosphorus.

Agricultural activities are a major nonpoint source of phosphorus in the Basin, and may also contribute significant quantities of sediment and some toxic substances, such as pesticides. While agricultural land accounts for only 14% of the Basin’s land area, it is estimated to contribute about 38% of the total nonpoint source phosphorus load to the Lake. Major sources of agricultural phosphorus are manure and commercial fertilizer runoff from fields, soil erosion, runoff from livestock concentration areas, milkhouse effluent, runoff from stacked manure, livestock access to streams and ponds, and streambank erosion from livestock.

Forests cover about two thirds (66%) of the Basin’s surface area, but contribute only 15% of the average annual nonpoint phosphorus load to Lake Champlain. Since approximately only one percent of the Basin’s commercial forests lands are harvested each year, forestry activities represent a very small percentage of the total pollutant load. Even so, tree harvesting and road construction can have significant local water quality impacts, such as stream sedimentation that can damage habitat for fish and other aquatic species. Therefore, careful management practices must still be followed.

[NOTE: This page was updated in 2008, based on the most recent technical report on land use that was released in 2007]


Learn More...

• LCBP Fact Sheet #2 - Nonpoint Source Pollution
• Urban Runoff Poster Series (LCBP)
• Updating the Lake Champlain Basin Land Use Data to Improve Prediction of Phosphorus Loading. LCBP Technical Report #54. May 2007.
• Background Technical Information for Opportunities for Action: An Evolving Plan for the Future of the Lake Champlain Basin. LCBP. LCBP Technical Report #16. June 1996.
• Lake Champlain Nonpoint Source Pollution Assessment. LCBP Technical Report #6. February 1994.
• Urban Nonpoint Pollution Source Assessment of the Greater Burlington Area. Urban Stormwater Characterization Project. LCBP Technical Report #25. December 1997
• Estimation of Lake Champlain Basinwide Nonpoint Source Phosphorus Export. LCBP Technical Report #31. September 1999.
• Benthic Phosphorus Cycling in Lake Champlain: Results of an Integrated Field Sampling/Water Quality Modeling Study. Part A: Water Quality Modeling HydroQual, Inc. LCBP Technical Report #34A. June 1999.
• Benthic Phosphorus Cycling in Lake Champlain: Results of an Integrated Field Sampling/Water Quality Modeling Study. Part B: Field Studies HydroQual, Inc. LCBP Technical Report #34B. June 1999.
• Determination and Quantification of Factors Controlling Pollutant Delivery from Agricultural Land to Streams in the Lake Champlain Basin J.W. Hughes, W.E. Jokela, D. Wang, C. Borer, UVM. LCBP Technical Report #35. September 1999.
• The Feeding of Supplemental Phosphorus on Dairy Farms in the Lake Champlain Basin: An Education/Demonstration Project. Kurt Cotanch, Catherine Ballard, Wanda Emerich, Charles Sniffen, and Everett Thomas; W.H. Miner Institute. LCBP Technical Report #42. April 2003.