Anton James Surunis

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Forest fires darken snow albedo and degrade forest structure altering snowpack energy balance, peak snow volume and snowmelt timing for up to 15 years following burn. To date, three-dimensional volumetric estimates of postfire effects on snow hydrology over the course of postfire recovery have not been quantified at the watershed scale. Here we present an improved parameterization of recovery of forest fire effects on snow hydrology. Using a spatially-distributed snow mass and energy balance model called SnowModel, we estimate volumetric shifts in snow-water storage and snowmelt timing across a chrono-sequence of eight burned forests occurring between 2000 and 2019. One to three years following fire, postfire effects reduced peak snow-water storage by 8.42% on average (sd = 9.38%) and advanced snow disappearance date by 34 days on average (sd = 7 days). Magnitudes of snow disappearance date advances tended to decline over recovery relative to the losses observed immediately following fire. Postfire reductions in peak snow-water equivalent (SWE) tended to decrease immediately following fire, and generally recovered over 15 years postfire, but then increased again 4 to 9 years later. Postfire reductions on peak SWE summed over the 15-year postfire recovery period were up to eighteen times greater than the losses incurred in the first winter following fire alone. Beyond 15 years following fire, postfire effects on snow persisted due to the postfire shift from forest to open meadow.