The 30,000-Foot View: Why It's So Tough To Keep Nutrient Pollution Out Of Lake Champlain
More than two-thirds of the problematic phosphorus overload in Lake Champlain comes from Vermont. To clean up its act the state recently signed Act 64, the Vermont Clean Water Act. It tackles runoff coming from sources varying from roofs and roads to forests and farms.
But there is no simple fix for keeping pollution out of the lake, in part due to the state’s vast network of waterways, hilly landscape and unique geography.
“A special characteristic of Lake Champlain is that the basin area around the lake is about 19 times larger than the water area of the lake itself,” says Breck Bowden, a professor of watershed science & planning at the University of Vermont. He points to a three-dimensional relief map of Lake Champlain at the ECHO Lake Aquarium and Science Center in downtown Burlington. It shows the long skinny lake surrounding by a giant basin of green encompassing parts of Vermont, New York and Canada. This whole land area flows into the lake.
“And if we compare that to some of our neighbor lakes like the Great Lakes to the west of us, that ratio for the Great Lakes is more like 3 or 4 to 1. So we have five times more area contributing sediment and nutrients nitrogen and phosphorus to the lake.”
And that, says Bowden, is part of what makes cleaning Lake Champlain so challenging.
Too much of a good thing
Phosphorous is of particular concern in Lake Champlain because it feeds the growth of sometimes toxic cyanobacteria, also known as blue-green algae.
While other nutrients, such as nitrogen, can also be polluting waterways when present in excess, Bowden says phosphorous is the limiting factor for algae growth.
“The best analogy that I can give us, let's say that you were trying to build a little work shed in your backyard,” says Bowden. He says you’d need plywood, two-by-fours and some nails — just like algae needs carbon, nitrogen and phosphorous.
“But you'd need only a few sheets of plywood, you need a lot more two-by-fours and you'd need a lot more nails to be able to put it together correctly. Living organisms are basically the same,” says Bowden. They need about 102 atoms of carbon for every 14 atoms of nitrogen for every atom of phosphorus.
“The blue green algae are very special," Bowden adds. "They can manufacture all the nitrogen that they need, so the limiting nutrient is phosphorous. If we give them phosphorous, they'll go crazy."
Surprising sources of nutrients
Bowden says we're just beginning to appreciate “the role of stream bank erosion and its ability to deliver phosphorous.”
He says this underappreciated source actually contributes about 25 percent of the phosphorous to Lake Champlain. Urban areas are also a disproportionately large contributor of phosphorous to the lake.
Forests contribute relatively small amounts of phosphorous, but Bowden says because Vermont has so much forested area that it cumulatively contributes a fair amount. That’s why the Vermont Clean Water Act outlines new rules to manage forests, and to regulate all roadways and large parking lots and roof areas for the first time.
A natural fix?
Researchers have experimented with building a “living machine,” a mix of plants that naturally uptake high levels of phosphorous, as a way of naturally restoring the balance of nutrients in our waterways.
Bowden says the “living machine” is a mix of algae and bacteria that are purposely cultured to remove waste from the sewage stream to produce water that is not drinkable but is clean enough to be released directly into a river.
“That type of technology exists at the scale of working in individual buildings — the idea of taking that all the way to a large lake is an interesting and challenging one,” says Bowden.
Hope for the future
Bowden says the nutrient pollution has gotten worse in recent years, and climate change will likely exacerbate the problem.
“I think it probably will get a little bit worse before it gets better, but I think that we're on the right track,” says Bowden.
He says it gives him hope that state residents, officials and organizations are in it for the long haul.
“We all have to work together, not pointing fingers at other people, but actually working together to solve this problem, or it will just get worse," he says.
Bowden points to the Vermont Clean Water Act and the new limits on phosphorus loading into the lake handed down form the Environmental Protection Agency as key pieces of legislation he thinks will have a real impact on the lake’s health.