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Publication Date
22 February 2022

Growing Impact of Wildfire on Western US Water Supply

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How will increasing wildfire activity affect water resources in the water-limited western United States? Among basins where more than 20% of forest burned, our study finds that postfire streamflow is significantly enhanced by an average of approximately 30% for 6 years after the fire event. Photo by Karsten Winegeart | Unsplash.

This study analyzed 72 forested basins across the western US that burned between 1984 and 2019 and showed the multi-basin mean streamflow was significantly elevated for an average of 6 water years postfire, compared to the range of results expected from climate alone. Researchers found that the streamflow response scales with fire extent: among the 29 basins where >20% of forest area burned in a year, streamflow over the first 6 water years postfire increased by 30%. Postfire streamflow increases were significant in all four seasons.


Historical fire-climate relationships combined with climate model projections suggest that 2021 to 2050 will see repeated years when the climate is more fire-conducive than in 2020, the year currently holding the modern record for forest area burned in the western US. The results suggest that burned areas will grow enough over the next 3 decades to enhance streamflow at regional scales.


Wildfire is an emerging driver of runoff change that will increasingly alter climate impacts on water supplies and runoff-related risks. Streamflow often increases after fires, but the persistence of this effect and its importance to present and future regional water resources are unclear. Researchers address this knowledge gap in the western United States, where annual forest fire areas increased by more than 1,100% from 1984 to 2020.

Point of Contact
Jason Smerdon
Columbia University
Funding Program Area(s)
Growing impact of wildfire on western US water supply
Williams, A. Park, Ben Livneh, Karen A. McKinnon, Winslow D. Hansen, Justin S. Mankin, Benjamin Cook, Jason E. Smerdon, et al. 2022. “Growing Impact Of Wildfire On Western Us Water Supply”. Proceedings Of The National Academy Of Sciences 119. doi:10.1073/pnas.2114069119.