Changes to Snow, Rain, and Dry Days in a Headwaters Basin to the Colorado River in a Future, Warmer Climate

Changes in water resources from the Colorado River are critical to quantify, given the contentious debates over allocating a dwindling water supply to a growing population that relies on it for agriculture, recreation, and livelihood. A headwaters basin to the Colorado River–the East-Taylor River Basin in Colorado–is selected to analyze future changes in snow, precipitation, and dryness over a 40-year period. A convection-permitting model dataset with a 4-km grid-spacing over the continental United States (CONUS404) shows good agreement with observations of cool-season precipitation amounts and trends from 1981–2021, and is used to analyze the future changes. Pseudo-global warming (PGW) simulations are run over the same period as CONUS404 from 1981–2021, but with perturbations from the 100-member ensemble mean of the Community Earth System Model2 Large Ensemble under SSP3-7.0 applied. We examine changes to the frequency of snow, rain, and dry days, the thermodynamic conditions, and the impacts on land surface fluxes in the PGW simulations compared to the historical simulations. Quantifying long-term changes to precipitation and dryness using convection-permitting simulations over the East-Taylor River Basin is critical information for water managers planning how to allocate future water supplies along the Colorado River in a warmer climate.