Landscape and Burn Severity Controls on Post-fire Snowpack Response in Montane Forests

Wildfire is becoming a more common landscape disturbance in snow-dominated watersheds as burned area extents have increased within high elevation areas that store key snow-water resources for down-stream communities. In snow-dominated watersheds, fire modifies the surface-energy budget that controls, in part, the magnitude and timing of snow accumulation and ablation. While there is growing recognition of fire-induced changes to seasonal snowpack dynamics, post-fire hydrologic studies have generally focused on changes in water quality or stream discharge as opposed to downstream impacts of fire-modified accumulation and ablation. To bridge these gaps, we use a combination of remotely sensed (i.e., satellite, fixed-wing), continuous plot-scale radiative and meteorological observations, and synoptic snow surveys to evaluate snowpack response to wildfire across a range of elevations, aspects, and canopy disturbances at several snapshots in time, and at eight continuously monitored north-south paired study sites. This approach demonstrated that topographic controls on snow distribution such as elevation and aspect still exhibit a stronger control on post-fire accumulation and ablation than wildfire induced changes. Nuanced radiative feedbacks also drove non-intuitive snow distribution patterns across burn-severities, particularly in areas where canopy was only partially combusted. In contrast, regions of lower burn severities where canopy remained unaffected, experienced insignificant changes in post-fire snow accumulation and ablation. Given the rising prominence of wildfire as a key land surface disturbance in snow-dominated watersheds, this work addresses key knowledge gaps currently inhibiting seasonal and long-term prediction of fire’s impact on snow water resources across burn-severities.