UVM agroecology fellow Nora Beer holds a Secchi disk, used to measure water clarity, on Lake Champlain on June 18. Photo by Kate Kampner
Researchers also announced the Lake Champlain Sea Grant was awarded just under $300,000 from the National Oceanic and Atmospheric Administration.
by Kate Kampner, Community News Service
Fair skies one Thursday a couple weeks ago might’ve suggested a good day on the lake for boaters. But toward the mouth of the Winooski River, a clear cut of gray across the blue waves was hard to miss.
Flooding again caused the river to overflow into Lake Champlain and with it came an influx of phosphorus and sediment such as dirt and bits of landscape. Together, fine particles from the debris created a string of murky, chocolate-colored plumes across the water.
The cloudy water will likely take about two weeks to clear up. That was according to several researchers hosting the equivalent of a floating press conference on the lake that morning. The five experts — several affiliated with the University of Vermont — took reporters on the college’s new hybrid-electric boat to talk about water quality risks to the lake.
The researchers also announced the Lake Champlain Sea Grant was awarded just under $300,000 from the National Oceanic and Atmospheric Administration to launch a community-action coalition focused on reducing plastic pollution into Lake Champlain.
A larger trend
One of the indicators of bad water quality can be raised counts of E. coli or chloroform bacteria, which are brought in with river sediment and hazardous if ingested. The plumes also prevent photosynthesizing organisms from getting the energy they need by limiting how much light fully passes through the water.
Matthew Vaughan, chief scientist of the Lake Champlain Basin Program, was surprised how the lake recovered after last year’s catastrophic floods.
“There’s a shorter timescale of recovery where the lake can bounce back, but in the long run we are battling against an increase in flow over time and more nutrients coming downstream,” he said.
Vaughan said last year on July 11, the Winooski River had the highest flow researchers had seen since 1990.
“When we ran the numbers, we determined that half of the annual phosphorus’ (total maximum daily load) was deposited in Lake Champlain in a week’s time from the storm last year,” he said, referencing the highest amount of the mineral the lake can take in a day before exceeding water quality standards.
With the flooding this month, the flow level reached the 10th highest measure since 1990, Vaughan said. “The flow overall of the lake was about two-thirds of what it was last year,” he said, and he expects the amount of phosphorus in the lake to be lower this year.
“Although we saw infrastructure damage, it was higher up in the watershed and in steeper areas,” he said.
Vaughan noted that this year’s extreme rainfall was a byproduct of Hurricane Beryl, the earliest Category 5 hurricane on record since the 1850s. Category 5 storms feature winds greater than 157 mph.
“This really can be tied to climate change, increasing air and ocean water temperatures, and that’s part of why you’re seeing an increase in flooding here in the Lake Champlain Basin,” he said. “It’s part of a larger trend.”
Devastating cycles
To determine water visibility, UVM researchers use a Secchi disk — a black-and-white disk that is lowered into the water until you lose sight of it.
In some of the most recent tests after the early July floods, disks disappeared at just 0.3 meters in one spot of the lake and 1.7 meters in another. A typical clear water average would be between 3.5 and 7.5 meters, Vaughan said.
Lake Champlain Sea Grant Director Anne Jefferson, a UVM professor, said flows that carry debris into the lake can sometimes be natural. “Rivers moving things like sediment and wood are natural and good processes; that dynamic landscape is a functioning landscape,” Jefferson said.
But when those flows pass through developed land, they can contort the natural processes into devastating cycles.
“Anytime that we’ve gotten water moving over our urban areas or causing erosion in the rural areas — taking out pieces of buildings or even just flowing over a parking lot in a heavy rainstorm,” she said, “we are picking up all of the human pollution, including trash, and delivering it to our streams and rivers and eventually Lake Champlain.”
Organisms can struggle to digest plastic, if they can at all, meaning it remains inside them and causes nutrition problems, Jefferson said. Plastics in the water also provide homes for bacteria and algae that otherwise wouldn’t get to set up colonies, she said.
Rebecca Diehl, a UVM research assistant professor, said it’s natural to regularly have a small amount of sediment moving through the watershed, but with extreme weather events, there’s an excessive amount of sediment and nutrients.
In her research, she looks at natural processes in the landscape that help mitigate sediment runoff. “Floodplains themselves, when they’re properly functioning … they can do a lot to slow floodwaters and capture those nutrients and sediments and keep them on the landscape.”
Last year, Vermont floodplains captured about six times more phosphorus than during more routine floods, Diehl said.
“If we open up our floodplains, if we can take advantage and harness that natural function, we potentially can put a dent in the massive amount of sediments that are moving through our landscape,” she said.
Via Community News Service, a University of Vermont journalism internship, on assignment for the Vermont Community Newspaper Group.
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