Ski Area Affects Mountain Watershed, Study Shows

Despite these new uses, most scientific studies of soil and water in high-elevation areas have focused on the effects of traditional resource extraction, like logging. How ski resort developments impact watersheds is little understood.

In the first study to document the effects of existing ski resort development on water flows and water quality in the northeastern US, Beverley Wemple, associate professor of geography at the University of Vermont, and her colleagues, have studied two side-by-side mountain watersheds on the eastern slopes of Mount Mansfield in Vermont. The nearly pristine Ranch Brook watershed served as a control, while the adjacent West Branch watershed contains the Stowe Mountain Resort.

Their results, forthcoming in the print edition of the journal Hydrological Processes (and published online April 24, 2007," show “surprising” differences, Wemple said, between the two watersheds, including greater water volume, chloride (probably from parking lot salt runoff) and sediment (probably from land clearing) flowing out of the developed watershed.

“Our results suggest the hydrologic effects of resort development may be more pronounced than the effects of timber extraction,” Wemple said.

The data presented in Hydrological Processes “will give us a baseline for evaluating the impacts of the new resort expansion that has taken place at Stowe in recent years,” she said, and is part of a long-term study there that “will provide scientific grounding for other proposed resort expansions in the region.”

The study analyzes data collected from 2001-2003. Next, the researchers are moving on to analyze the data they have been collecting during a major expansion of the ski area that began in 2004.

“We’re concerned that folks are going to interpret these results to say, ‘this is all the ski area’ or ‘the ski area is a problem.’ But we can’t—and don’t—say that. We’re just laying out what we’re seeing,” said James Shanley, one of Wemple’s co-authors, who works for the US Geological Survey in Montpelier. For example, he points out that a considerable portion of the water volume differences may be caused by natural variation between the two watersheds.

And “the ski areas may be pleased by these results because there are no glaring water quality impacts that we show are connected to the existence of the ski area,” he said.

Nevertheless, “There is a lot more water coming off this developed watershed than we would have thought originally,” Wemple said and a “measurable” amount of change in the water flowing through the West Branch watershed can be attributed to the ski area. In the developed watershed, water yields were 18-36% higher than the control, chloride about ten times higher than a natural forest basin, and suspended sediment more than two and half times greater.

“The way we deal with that, when we do development, is to plan for more stormwater than we have traditionally or than existing studies suggest we should,” Wemple said. “If we know what we’re dealing with, we can design for effective stormwater management on the side of Mount Mansfield as well as we can in Ferrisburgh.”

Whether the new ski lifts, vacation homes, and other developments built at Stowe in the last three years will produce big changes in the hydrology of the West Branch watershed remains to be seen. “Our results from after the expansion began won’t be published for a couple of years,” Shanley said.

In any case, Wemple says one of overarching lessons of her study is that “we need more information about stormwater management in the mountain environment.”