After wildfires, scorched trees could disrupt #water supplies — The Associated Press #wildfire

Watershed Assessment Vulnerability Evaluation (WAVE) volunteers work to install silt fencing immediately above Northern Water’s Willow Creek Reservoir. Photo by Emanuel Deleon, Colorado State University

Click the link to read the article on the Associated Press website (Brittany Peterson). Here’s an excerpt:

In a California forest torched by wildfire last summer, researcher Anne Nolin examines a handful of the season’s remaining snow, now darkened by black specks from the burned trees above. Spring heat waves had already melted much of the year’s limited snowfall across California and parts of the West when Nolin visited in early April. But she and her colleague are studying another factor that might’ve made the snow vanish faster in the central Sierra Nevada — the scorched trees, which no longer provide much shade and are shedding flecks of carbon.

Albedo effect

The darkened snow is “primed to absorb all that sunlight” and melt faster, said Nolin, who researches snow at the University of Nevada, Reno. As climate change fuels the spread of wildfires across the West, researchers want to know how the dual effect might disrupt water supplies. Communities often rely on melting snow in the spring to replenish reservoirs during dryer months. If snow melts earlier than normal, that would likely leave less water flowing in the summer when it’s most needed, Nolin said.

Multiple studies indicate that snow in a burned forest disappears up to several weeks sooner than snow in a healthy forest because of the lack of a shade canopy and carbon shedding from trees that intensifies the absorption of sunlight. Water forecasting factors in variables including snow density, soil moisture and air temperature. Although dark accumulation on snow isn’t widely measured, Tim Bardsley, a hydrologist with the National Weather Service, said it is a contributing factor to the timing of snowmelt and is worth considering incorporating into supply forecasting. Dust, ash and soot similarly affect snow by causing it to absorb more light in what’s known as the “albedo effect.” But California officials are increasingly worried about carbon, which absorbs even more.

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