2024 Abstracts

Seasonal Cycles Unravel Mysteries of Missing Mountain Water


Jessica Lundquist1* (jdlund@uw.edu), Ethan Gutmann2, Rosemary Carroll3


1University of Washington, Seattle, WA; 2National Center for Atmospheric Research, Boulder, CO; 3Desert Research Institute, Reno, NV



Snow provides over 60% of water supplies in the western United States, and in general, spring snow measurements provide a good prediction of summer streamflow. However, in some years, these streamflow predictions are not accurate, and water managers struggle to efficiently allocate water resources. In many studies, warming temperatures correspond to less observed streamflow per unit precipitation input. However, key elements, including basin heterogeneity, gauge undercatch, groundwater flow, and water storage, are often not represented in models or predictions, and physical hydrologic models diverge widely in their hydrologic sensitivity to warming. The project describes distributed observations in the well-instrumented East River (Colorado) and Tuolumne River (California) basins combined with modeling that researchers are using to investigate snow distribution as a function of elevation and snow heterogeneity. The team hypothesizes that more uniformly distributed snow cover leads to greater subsurface water connectivity and more efficient water delivery to the stream. More variable snow cover, either through a greater elevational gradient or increased patchiness, leads to less effective recharge and greater evaporative losses. Only modeling that represents subsurface water transfer from snow-covered to snow-free grid cells will be able to represent these effects.