Forest fires decrease the volume of snow-water storage and advance the timing of snowmelt across the western U.S.

Abstract:

Mountain snowpack seasonally stores the majority of annual water resources in the western United States. The extent, duration, frequency, and intensity of forest fires are increasing across the western U.S. as a result of climate change and fire suppression, making it more important than ever to understand how these changes are impacting snow-water storage and the associated water resource availability. Using long-term data from 85 SNOTEL snow monitoring stations across eleven western states and Alaska, we characterize changes in snow accumulation, storage, and melt as a result of forest fire occurrence. We evaluated peak snow water equivalent (peak SWE), snowmelt rate (SMR), and snow disappearance date (SDD) before and after forest fires occurred. Our results indicate that forest fires significantly decreased peak SWE by 3.5 cm and advanced SDD by 9 days on average across all sites in the western U.S. for 10 years following a fire, with the most profound impact observed in the Southwestern region. Forest fires alter the volume of snow accumulation and timing of snowmelt and associated downstream water resources. This empirical investigation informs water resource management and modeling of future water resource availability in burned forested mountainous headwaters.