ADDISON COUNTY — As floodwaters in Lake Champlain recede, groups across the state are paying close attention to water quality issues in Vermont’s largest body of water.
It’s already clear that phosphorous and sediment levels are high in the lake, and that flooding and high winds have caused a great deal of shoreline erosion, according to Bill Howland, manager of the Lake Champlain Basin Program in Grand Isle.
“This year, we’ve had particles as well as nutrients going into the lake in unprecedented amounts,” he said. “Certainly not in this period of history have we seen anything as severe as this year.”
The Lake Champlain Basin Program in Grand Isle works closely with the Vermont Department of Environmental Conservation to monitor phosphorous and sediment levels in the lake at all times, but especially after large storms.
“With so many storms (this spring), we’ve had to monitor more frequently than usual,” Howland said.
He said the phosphorous runoff comes from a combination of agricultural and urban sources, with a minimal amount also washing out of the forests at the higher elevations.
And while excess phosphorous levels do fuel toxic algae blooms in the lake, Howland also said it would be overly simplistic to assume that high levels of phosphorous will lead to higher levels of algae this summer. The sediment in the water, he said, is blocking the rays of the sun from extending very deep, meaning that the lake is also cooler than usual — not an ideal condition for algae bloom.
In fact, said Howland, the scientific effect of this spring’s heavy rains won’t be clear for some time yet. The state collects data, but that data will not be analyzed and released until the end of the year.
While the LCBP monitors at the outlets of rivers on Lake Champlain, others are keeping track of data further upstream. Marty Illick of the Lewis Creek Association said the tributaries that feed the lake have seen effects of this year’s flooding as well, and that phosphorous and sediment levels have been high on all of the streams and rivers that feed Otter Creek. There’s been erosion on the banks of some waterways due to the high volume of water flowing toward the lake, and excess sedimentation isn’t always healthy for the insects and fish that live in the stream.
“It’s really the flat valley area that is the most vulnerable to erosion, soil movement and pollution,” Illick said, clarifying that pollution can come in the form of both nutrients and sediment.
Because the flat areas have been cultivated as agricultural land for hundreds of years, she said the early- and mid-century farming practices of straightening streams for irrigation, planting over wetlands and digging runoff ditches come back with a vengeance during flooding now, when sediment and phosphorous that would otherwise be filtered out of the water head straight into Lake Champlain.
Despite a focus on agricultural runoff, however, the 2008 State of the Lake report by the Lake Champlain Basin Program found that less than half of the phosphorous reaching the lake in the Otter Creek tributary comes from agricultural sources. About half of the phosphorous runoff is from developed sources, which includes lawns, roads and buildings.
And Illick said severe weather events cause significant changes to waterways and land. She said global climate change could further accelerate this process, accentuating the need for conscious land management.
“This is changing the shape of our stream channels — they’re getting bigger. That means more sediment and different flood plains,” she said. “We’re going to have to take extra measures to not only monitor but to come up with better management practices.”
Because the flooding came so early in the spring, water washed across fields taking valuable nutrients away and preventing farmers from planting on those fields — which in turn promoted more sediment erosion.
“Because those fields are bare, (water) is just going to keep picking up those soil particles,” she said.
Regardless, the best way to prevent runoff, said Illick, is to make sure that as much land as possible — from fields to lawns to runoff ditches — is planted with grass or another cover crop.
LAKE RECREATION
The high water levels have raised some concerns as the recreation season draws near.
The National Oceanographic and Atmospheric Association is warning boaters to be cautious of an excess of debris floating in the water in some areas, and Howland said the state is keeping a close eye on waterways, monitoring for possible bacterial contamination coming downstream from failed septic systems or wastewater management plants that overflowed.
But Craig Whipple, director of state parks for Vermont State Parks and Recreation, said the monitoring has found no unusual results for bacteria in the areas of state parks and beaches. While some lakefront parks further north remain closed due to high water levels, all Addison County parks — both on Lake Champlain and further inland — opened over Memorial Day weekend as planned, and all tested below required levels for e. coli bacteria.
Reporter Andrea Suozzo is at [email protected].