Growing Impact of Wildfire on Western United States Water Supply
Abstract
Streamflow often increases after fire, but the persistence of this effect and its importance on present and future regional water resources are unclear. This could be critical in the water-limited western United States (WUS), where annual forest-fire area increased by >1100% since 1984 and repeated extreme hydroclimatic swings during this time have caused both severe drought and flooding events. Here we find that among 72 minimally managed, forested basins across the WUS that burned between 1984 and 2019, mean streamflow was significantly elevated for an average of 6 years post-fire compared to expectations from climate alone. Significance is assessed by comparing pre- and post-fire streamflow responses to climate and also by comparing post-fire streamflow among burned basins to concurrent streamflow among 108 control basins that did not burn during the study period. Among the 40% of burned basins that were most heavily burned, the 6-year post-fire streamflow increase was 2030% and it was significant in all four seasons. Historical fire-aridity relationships combine with climate-model projections to suggest that 20212050 will see repeated single-year burned areas that greatly exceed that of the extreme 2020 wildfire season. This would cause entire regions to experience significantly more runoff than expected based on pre-fire streamflow responses to climate. Wildfire is an emerging driver of runoff change that will increasingly alter climate impacts on water supplies and runoff-related risks across the region.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMGC52A..01W