This story by Aaron Calvin was first published in News & Citizen on Dec. 24, 2025.
This winter the University of Vermont marks a quarter century of continuous research documenting two key tributaries of Mount Mansfield — the West Branch of the Little River and Ranch Brook.
After 25 years, researchers have a clearer picture of the changes in runoff on the mountain, where a warming climate continues to drive a trend of winter contraction, meaning a later first snowfall and earlier spring melt.
When UVM professors Jamie Shanley and Beverley Wemple began monitoring Mount Mansfield, they found an ideal juxtaposition for an experiment: On the one hand, the West Branch, with its anthropogenic impacts from the Stowe Mountain Resort and its development, and on the other The Ranch Brook, which has escaped the resort’s impact.
“It was kind of an ideal of a paired watershed study, where you have your control watershed — which should just march along and just be affected by climate and weather and everything — and then the developed watershed, your experimental watershed, which has all the development in it,” Shanley said.
The long-term study has offered some counter-intuitive results, including a refutation of Shanley’s original hypothesis. The West Branch has not shown evidence of the ski resort’s impact, as he had figured. Even the expected levels of chlorine from winter salt treatment were reduced after the state began introducing new stormwater runoff regulations.
“We really did not see a whole lot of effect of the ski resort on the stream chemistry or flow,” Shanley said. “We thought we might see a big smoking gun of, ‘Oh, yeah, they’re causing all kinds of problems in the stream,’ but we didn’t see a huge impact.”
Shanley and Wempel, along with UVM geoscientist Andrew Schroth and lead author Kate Hale — a University of British Columbia professor and a former UVM post-doctoral researcher — published a paper in February’s issue of the academic journal Hydrological Processes looking at the relationship between snowpack decline on Mount Mansfield, warming winters and increases in annual and seasonal runoff.
Long-term cumulative data collected by the National Weather Service at the Mount Mansfield snow stake, installed in 1954, has revealed that the snow season has shrunk by almost three weeks since 1965, with snowpack onset occurring later in the fall months and disappearing earlier in the spring months. Winter rain-on-snow events, which occur at warmer temperatures, have also increased.
This weakening of the snowpack is having under-studied impacts on the broader regions’ waterways, including an increased risk of mid-winter flooding and summer drought.
