Forests and phosphorus reduction in Lake Champlain
ADDISON COUNTY — The Environmental Protection Agency has estimated that forest lands account for about 16 percent of the phosphorus going into Lake Champlain for the entire Vermont portion of the lake.
In the Otter Creek watershed, the watershed that covers most of Addison County, the figure is estimated to be just slightly higher, at 17.1 percent. This slightly higher number reflects the portion of the Otter Creek watershed that is forested, which the Department of Environmental Conservation gauges at around 60 percent.
Phosphorus sources vary from watershed to watershed, depending on the geography and industry in a particular region. Statewide, estimated phosphorus contributions from forest land can run as high as 35 percent for the Missisquoi Bay lake segment and as low as 0 percent for the Cumberland Bay lake segment.
According to the EPA’s estimates, forest lands are the second-largest contributor of phosphorus within the Otter Creek watershed, next to agriculture. The EPA estimates phosphorus sources within the Otter Creek watershed overall as:
• Agriculture, 49 percent.
• Forest lands, 17.1 percent.
• Stream erosion, 16.4 percent.
• Developed lands (parking lots, roads both paved and unpaved, roofs, large athletic fields), 14.4 percent.
• Wastewater treatment facilities, 3.2 percent.
Department of Forests, Parks and Recreation Forestry District Manager Gary Sabourin said that the EPA estimates were based on modeling for all sectors.
“There hasn’t been a lot of research done on phosphorus contribution from forest land. I’ve got to think it’s relatively low per unit area,” Sabourin said. “But because forest land covers such a huge amount of the basin it represents a fairly large source of phosphorus in some watersheds.”
For most watersheds, including Otter Creek, the Vermont Total Maximum Daily Load (TMDL) Implementation Plan requires a 5 percent reduction in phosphorus from forest lands. In the Missisquoi Bay and in the lake segment known as South Lake B (south of Addison County), the plan calls for 50 and 40 percent reductions, respectively, given the water quality concerns in those watersheds.
Looking at other sectors in the Otter Creek watershed, Vermont implementation calls for an 80 percent reduction from what’s called “agricultural production areas” (barns and places where animals are concentrated), a 47 percent reduction from fields and pastures, a 40 percent reduction in streambank erosion and a 15 percent reduction from developed land.
As stressed in a recent TMDL fact sheet from the Department of Environmental Conservation: “All sectors contribute to water quality degradation in Lake Champlain, and all sectors must be part of the solution. Plans to implement the Lake Champlain TMDL involve new and increased efforts from nearly every sector of society, including homeowners, developers, farmers, municipalities, and state government.”
Reporter Gaen Murphree is reached at [email protected].