Potential Effects of a Warming Climate on Water Resources within the Lehman and Baker Creek Drainages, Great Basin National Park, Nevada
AuthorVolk, John Michael
AdvisorPrudic, David E
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Warming trends in near-surface air temperature across the Southwestern U.S. have been observed over the last century and are projected to continue over the 21st century. This warming trend will result in decreased snowpack and earlier snowmelt in mountainous basins throughout the West; however, predictions of future precipitation in the Southwest are much more uncertain among global climate models (GCMs). In this study, the objective was to quantitatively evaluate the impacts of projected warming on streamflow in the Lehman and Baker Creek drainages. The drainages are located in Great Basin National Park that encompasses the highest elevations in the southern part of the Snake Range in eastern Nevada. The Precipitation-Runoff Modeling System (PRMS) was used to evaluate impacts of warming on streamflow. Calibration and validation periods had total errors between 0.6 and 12 percent in simulated streamflow. Daily maximum and minimum temperatures for a future 90-year period were used in the model to evaluate how warming temperatures may affect streamflow. Daily temperatures were statistically downscaled and bias corrected using daily projections from the National Center for Atmospheric Research Community Climate System Model 4.0 for four representative greenhouse gas concentration trajectories. A 30-year record of historical precipitation was repeated three times over the 90-year simulation. Results from the 90-year simulation were divided into three 30-year periods (water years 2009-2038, 2039-2068, and 2069-2098) and were compared among the four greenhouse gas concentration trajectories such that volumes and variations in precipitation were identical and changes could be directly related to different projected warming temperatures. The study area was sensitive to small increases in temperature; results include shifts to earlier snowmelt timing for most warming trajectories from May to April with an increase in winter streamflow. For a temperature rise of 5.5°F by the end of the century, mean annual streamflow was reduced more than 10 percent and resulted in a corresponding increase in evapotranspiration; also a significant decrease in peak snowpack and May runoff was simulated. Reduced snowpack and earlier snowmelt affected the snow-dominated watersheds by reducing soil moisture and evapotranspiration in July and August.