HYDROLOGIC RESPONSE OF THE GALLINAS RIVER TO THE 2023 SPRING SNOWMELT POST-2022 HERMITS PEAK/CALF CANYON FIRE

Forest fires are well known to impact the quality of water in a watershed from hillside erosion and fire sedimentation as well as the quantity of water entering the system from decreased soil infiltration, lessened vegetation interception, and increased catchment evapotranspiration. The Gallinas Watershed in northern New Mexico was impacted by the 2022 Hermits Peak/Calf Canyon (HP/CC) Fire, the largest wildfire in New Mexico’s history (>340,000 acres). Approximately 115,542 acres burned in the Headwaters Gallinas River Watershed, 21% of which were classified by the USFS Burned Area Emergency Response team as high burn severity. While much research focuses on the increased flooding from monsoonal rains after a forest fire, little data exists about the hydrologic impacts from spring snowmelt runoff. This study tested the hypothesis that post-fire conditions would lead to earlier snow disappearance in the burned watersheds and flashy runoff on the spring hydrograph. We monitored in near real-time the snow water equivalent (SWE), air temperature, and soil moisture in the Gallinas Watershed headwaters (Wesner Springs SNOTEL site) and compared them to amounts and trends in discharge within Gallinas Creek near Montezuma, NM (USGS gaging station 08380500). We looked at historical data as well, with emphasis on the period during the spring snowmelt (March through May) to assess what if any impact the 2022 HP/CC fire had on hydrologic conditions. Historically, the Gallinas Creek hydrograph shows a shallow slope during the winter low-flow period, increases stepwise in response to spring warming, then decreases broadly and diffusely during late spring to early summer with intermittent peaks related to rain events. The 2023 Gallinas River hydrograph pattern is consistent with its historical trend suggesting that post-fire, the watershed has maintained resiliency to snowpack retention and water storage. Continued monitoring in near real-time is imperative to forecast flood stages, manage fire sedimentation, and protect water supplies.