Slower snowmelt affects downstream water availability in western mountains

From University of Nevada, Reno:

IMAGE: Ecohydrologist Adrian Harpold from the Universitiy of Nevada, Reno’s College of Agriculture, Biotechnology and Natural Resources takes measurements of the Sierra Nevada mountain snowpack. He studies impacts of the Sierra… view more

Credit: Photo courtesy of University of Nevada, Reno.

RENO, Nev. – Western communities are facing effects of a warming climate with slower and earlier snowmelt reducing streamflows and possibly the amount of water reaching reservoirs used for drinking water and agriculture, according to a study published in July.

“As the climate warms, there is actually a slower snowmelt – both in timing and rates, which makes for a less efficient streamflow,” Adrian Harpold, ecohydrologist at the University of Nevada, Reno said. Harpold, who initiated the study two years ago at the University of Colorado Boulder, is a co-author of the paper published in AGU publications Geophysical Research Letters.

“I know, it’s counterintuitive, but with a warming climate snowmelt starts sooner in the season, and at a slower rate because the warming occurs earlier when days are shorter and we have less sunlight,” he said. “What makes runoff less efficient is that slower snowmelt reduces the amount of moisture being pushed deep into the subsurface where it is less likely to evaporate”

Higher snow melt rates can develop a pressure gradient that forces moisture deeper into the ground. With lower snow melt rates less water leaves the subsurface where the root systems of trees, bushes and grasses can access the water, which increases the amount of evapotranspiration into the atmosphere.

“It’s ubiquitous in the western U.S.; the trends are consistent to all mountain ranges across the West,” Harpold said.

Harpold, who’s Nevada Mountain Ecohydrology Lab is based in the College of Agriculture, Biotechnology and Natural Resources, continued to work with the team from …

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