New $800,000 study provides path to reducing lake pollution
Written by Candace Page, Burlington Free Press
Changing farm practices on that high-risk 20 percent of land would produce a two to three times greater reduction in phosphorus than making similar changes on fields chosen at random, the study found.
The three-year study collected data and used computer models to identify the areas of land in the Missisquoi Bay watershed with the potential to release the most phosphorus, a nutrient that drives noxious algae blooms in northern Lake Champlain.
These “critical source areas” cover only 20 percent of land that drains to the bay, but they may release 74 percent of the phosphorus in runoff. Changing farm practices on that high-risk 20 percent of land would produce a two to three times greater reduction in phosphorus than making similar changes on fields chosen at random, the study found.
“This can help us target and set priorities. It is a tool, but it is not the answer,” Julie Moore, an author of the report, told 40 people gathered Wednesday night to hear the results of the three-year study. Moore is a water resources engineer at Stone Environmental Inc., and former director of the state’s Lake Champlain clean-up program.
Among the study’s other key findings:
• Erosion of streambanks makes a larger contribution to phosphorus pollution than previously thought. The study found that bank erosion delivered 42 percent of the sediment and 39 percent of the phosphorus reaching the bay.
• The remaining phosphorus load, about 60 percent, comes from land runoff. In the farm-rich Missisquoi Bay basin, farms contributed two-thirds of that phosphorus, developed land only 6 percent.