Wildfires Threaten Future Water Supplies in the Western U.S.

By Climate Adaptation Science Centers

Across the West, wildfires are expected to increase in frequency, size, and severity. Not only is fire a threat to life and property, but it can also reduce the quality of water supplies by increasing the amount of sediment entering streams – turning clear mountain waters brown. These impacts to watersheds can persist for years and require costly restoration activities.

What:

Wildfires increase soil erosion because bare ground is exposed after vegetation burns. This enables rainfall and snowmelt to rush across the ground surface and carry large amounts of sediment into rivers and streams. To determine how future water supplies in the West could be impacted by fire, researchers modeled future wildfire activity through 2050, using projections of how climate change might alter the number and size of fires. Researchers then estimated the amount of soil erosion that would result from these fires and produced the first assessment of future fire-induced soil erosion for the region.

Findings:

Increasing wildfires could double soil erosion in a quarter of western watersheds by 2050, degrading water quality in these streams. Soil erosion could be particularly high in northern California and the mountainous areas of southern California, where fire frequency, size, and severity are expected to greatly increase. The Colorado Front Range could also see high increases in soil erosion with just small increases in fire because of the area’s steep mountainous terrain.

Significance:

Soil sediment that is washed into rivers and streams following fires contain minerals, nutrients, and metals that can be toxic to humans and wildlife if consumed in large quantities. Large amounts of sediment can alter stream flows, settle in reservoirs, or obstruct culverts. The cost of restoring watersheds following fire can be in excess of several million dollars.

Identifying watersheds threatened by increased soil erosion provides valuable insight to federal and state agencies in the West seeking to prioritize fire management activities and reduce the harmful and costly effects of fire on water resources.

Who:

Project Lead: Northwest Climate Adaptation Science Center

Partners: USGS Western Geographic Science Center | USGS Geosciences and Environmental Change Science Center | U.S. Forest Service | Boise State University

Stakeholders: U.S. Forest Service | USGS | National Park Service

Learn More:

Learn more about this project here

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