Snow Melts Fast in Wildfire Burn Areas, Imperiling Water Supply

Snow is melting faster in Western US forests scorched by wildfire, threatening drinking water supplies as climate change grips the region, according to research published Wednesday in the journal Science Advances.

Mountain snowpack, the source of 70% of the West’s water supplies, melts more quickly in spring the years after a wildfire scorches a forest than before the blaze, and the pace of melt increases, making water more difficult for water supply reservoirs to capture, according to the study conducted by researchers at the Colorado School of Mines.

The findings stand to influence federal wildfire policy as the Trump administration dismisses efforts to address climate change, reorganizes federal agencies that respond to wildfires, and promotes widespread logging on federal land in part to reduce wildfire threats. The Interior Department announced Monday it’s creating the US Wildfire Service, which will unify all federal firefighting efforts by 2026.

Much of the West’s water infrastructure runs on the rhythm and pacing of the spring snowmelt season. Snowmelt runs off into streams, and the water is captured in reservoirs, which store water for drinking or release it when it’s needed for irrigation. If snowmelt comes too fast or too soon, reservoirs may not be able to store or release the water at the right time.

“If our snow is melting earlier, it disrupts systems for capturing and forecasting water” runoff from spring snowmelt, said Arielle Koshkin, a researcher at the Colorado School of Mines and lead author of the study.

The research is among the first to show regional variations in the speed of snowmelt in forests burned in a wildfire, she said.

Soot and black carbon raining down from scorched trees melt snow quickly because it absorbs heat from the newly-open canopy of a wildfire-stricken forest, the study shows. Rising temperatures, which stand to reduce mountain snowpack 75% by 2100 across the West, stand to speed up the melting process even more. Together, those forces melt snow up to two weeks sooner after a wildfire than before it, especially in the Pacific Northwest and California, the study shows.

The effect is less pronounced in the Rocky Mountains because snow piles up at greater depths in burn areas at higher elevations after a forest canopy is incinerated, the study shows.

But wildfires are burning in higher elevations because of climate change, pushing them into mountain areas where snow persists all winter—essential sources of water for many Western cities, according to the study.

In warmer regions, snowpack can melt away from burn areas in the middle of winter, the study shows.

“The areas that were already vulnerable are going to be the most exacerbated in the future,” Koshkin said.