VT EPSCoR Looks at Warming Winters and Water Pollution

Climate change is leading to warmer winters, and that warmth means potential troubles for lakes and rivers in the United States. A recent publication in Environmental Research Letters from a multi-institutional team that includes several members of Vermont EPSCoR's BREE group examined the data behind this phenomenon in more depth.

The Changing Face of Winter Runoff

Vermont winters used to feature frozen ground and relatively consistent precipitation—snowfall would be the dominant precipitation for most of the winter, with rain-on-snow events somewhat rare. But now these rain-on-snow events are becoming more common, leading to an increase in nitrogen and phosphorous that feeds blue-green algae and other water pollutants.



"We are clearly seeing much larger amounts of cloudy water and sediment traveling through U.S. watersheds in winter," said BREE researcher Carol Adair, PhD. "The idea of winter nutrient pollution is new, because it's a relatively recent impact of climate change with the potential to cause significant problems for people and the environment—from algae blooms that make swimming dangerous to ‘dead zones' that kill fish stocks."

Impact Across the United States

The new research found that 40% of the US is currently producing winter pollution. This data calls for swift action. “No one is tracking exactly how much [winter pollution], where it's going, or the impacts on water quality and ecosystems," said Adair. “That's a big problem that urgently needs addressing.”


Rain-on-snow frequency and its effects in the US

Winters are currently the fastest warming season across the US. Days when the temperature drops below freezing (32 degrees Fahrenheit) are declining throughout the country, including places like Vermont which used to be famous—or infamous—for its brutally cold winter weather.

Where to Go from Here

This multi-institutional research is the first large-scale study of the impact of rain-on-snow on water quality. Because of this first of its kind status, the findings erred on the conservative side. That means that additional risks, such as snowmelt, winter rainfall events, and winter runoff's impact on downstream communities were not included.

In other words, the study's warnings should be taken to heart, because it may be worse than it seems on first blush. The more we learn about this phenomenon, the faster we can take action.

The study, “Winter runoff events pose an unquantified continental scale risk of high wintertime nutrient export,” was supported by the National Science Foundation (NSF EAR2012080, EAR2012123), the National Oceanic and Atmospheric Administration (NOAA NA19OAR4310280), and the Lake Champlain Basin Program and Vermont EPSCoR (NSF OIA #1556770).