Effects of forest management on snow accumulation and ablation in a montane watershed

Abstract

Forest management and thinning have implications on snowpack accumulation and melt dynamics. Changes to canopy cover alter snow interception, incoming radiation, and the cumulative energy balance. Bozeman, Montana, USA, receives up to 40% of its municipal water supply from the Bozeman Creek Watershed (45.5°N, 111°W), characterized by a densely overstocked forest that poses a high wildfire risk and subsequent impacts on the water supply. Although this watershed is of great importance and snowmelt dominated, the impacts of current forest thinning on the snowpack are not well understood. To examine how forest treatments aimed at reducing wildfire risk affect snow accumulation and melt, three key datasets with varying spatial and temporal resolutions were collected and analyzed. Measurements of snow depth from Uncrewed Aerial Vehicle (UAV) - based Light Detection and Ranging (LiDAR), weather from meteorological stations, and Sentinel-1 C-band Synthetic Aperture Radar (SAR) were collected and analyzed from treated and untreated plots of forest. SAR analysis suggests that the onset of melt initiates earlier and melts faster in the treated forest compared to the untreated forest, suggesting that the day of onset melt is influenced by canopy cover change due to forest thinning. The meteorological data also suggest a temperature or relative humidity difference between the treated and untreated forest. LiDAR-derived snow depth data demonstrate consistently more snow accumulation in the treated forest. Under current climate trends and continued land cover disturbances, this research will help shape better-informed forest management strategies that optimize forest health and water supply.