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University of Vermont study finds warming winters pose a threat to water quality in most U.S. states

A dark and swolen river runs over ice and snow along a flooded road, mountains in the back. It's winter and the sky is gray.
Wilson Ring
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The Associated Press
Water from the Winooski River runs over Vermont's Route 2, during a rain on snow event in February, 2016. It's the sort of event Vermont is poised to see more of due to climate change, and a new study from UVM finds there could be big consequences for water quality.

A new study from the University of Vermont finds warming winters present a serious threat to water quality in more than 40 states across the country.

The researchers — from the University of Colorado, University of Kansas, University of Michigan and University of Vermont — say New England and the Midwest are particularly at risk.

Climate change is making New England winters warm rapidly, bringing more rain on snow.

In fact, Vermont’s latest Climate Assessment shows the state is warming faster, on average, than the rest of the globe.

On top of that, many New England states have rich soils, full of phosphorus and nitrogen. In the past, those nutrients would reliably stay put under the snow until spring.

Carol Adair with the University of Vermont says that's no longer the case.

"Throughout Vermont and throughout the northeast, really, we're seeing... as much as, you know, five or six rain-on-snow events in a year,” Adair said. “And relative to the rest of the country, that's pretty high."

Most research on nutrient runoff in cold climates with consistent snow has historically focused on the growing season, the researchers found. Their study suggests that should change.

According to Vermont's Department of Environmental Conservation, phosphorous runoff is the leading threat to water quality in Lake Champlain.

Adair says her research shows these events are more polluting than big summer rainstorms, which Vermont is also expected to see more of as the climate warms — though modeling suggests there’s still time for that trend to correct itself if the world acts fast to cut global greenhouse gas emissions.

More from NPR: It's not too late to stave off the climate crisis, U.N. report finds. Here's how

For example, if the world does nothing to curb greenhouse gas emissions, it’s likely Vermont’s $1.6 billion ski industry will no longer be viable by 2080, due to a shortened season from lack of snow and cold temperatures. In contrast, the state’s climate assessment finds most ski areas will survive this century if the world acts fast to curb emissions.

Adair teamed up with colleagues at several universities to map where these rain on snow events are happening most, and which parts of the country have the most nutrients to shed.

uvm-study-water-quality-courtesy-20221014.jpg
University of Vermont, Courtesy
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A new collaborative study from UVM's Gund Institute and several other institutions found water quality in over 40 states is at risk for winter nitrogen and phosphorus pollution from rain-on-snow events driven by climate change.

New England is at risk of facing serious water quality impacts. But she says there are things farmers can do to help, like cover cropping and spreading their manure strategically to avoid runoff events.

“The other thing that’s very interesting about winter events is that from the limited data that we have, and from what we know about winter events and what they carry downstream, a winter event seems to carry more stuff, more sediment, more nutrients downstream than a similar event would during the growing season,” Adair said. “So, the same cubic foot of water in the winter is carrying more stuff than the same cubic foot during the summer.”

Adair says more research is needed to understand why this is the case, but she and her colleagues believe it has to do with the fact that plants are dormant in the winter.

“Trees are really good at taking up nutrients, as are other plants,” Adair said. “They can really tamp down on what leaves a [water] system, and we just don’t have that helping us out in the winter.”

Adair says it’s not clear how far those extra nutrients travel, and more research is needed to know whether some states are bearing the brunt of this extra winter pollution than others.

However, she says this is a problem we have the tools to fix — through cutting greenhouse gas emissions and adaptation.

“We just need to get the resources in place to be able to do that,” she said. “There are tools out there that can help us keep our nutrients on land, rather than in the streams.”

Have questions, comments or tips? Send us a message or get in touch with climate and environment reporter Abagael Giles @AbagaelGiles.

Abagael is Vermont Public's climate change and environment reporter. She joined Vermont Public in 2020. Previously, she was the assistant editor at Vermont Sports and Vermont Ski + Ride magazines. She covered dairy and agriculture for The Addison Independent and got her start covering land use, water and the Los Angeles Aqueduct for The Sheet: News, Views & Culture of the Eastern Sierra in Mammoth Lakes, Ca.