Study of climate change impacts of the upper colorado river basin on water resources and hydropower production, A

Abstract

The Upper Colorado River Basin (UCRB), comprised of the Colorado and Gunnison River basins, is regulated by 17 major reservoirs to provide water supply, flood control, and hydropower. It is the prime water source for much of the western United States, as well as key wildlife and fish habitat. Climate change is an issue of concern on the basin due to the sensitivity of snow accumulation processes that dominate runoff generation within the region. Climate models project an average warming of up to 4 degrees F, coupled with a decline in precipitation falling as snow. There is no numerical consensus of the magnitude of change in precipitation, but there is general agreement that precipitation changes will be exacerbated by increased evapotranspiration rates, reducing overall runoff. This is expected to cause a decline in runoff and hydropower generation capacity. Potential impacts of climate change on the hydrology and water resources of the UCRB were assessed through a comparison of simulated stream flow, temperatures, and reservoir volumes and storage levels. Future climate conditions derived from climate centers: Meteorological Research Institute (MRI-CGCM2.3.2), Canadian Centre for Climate Modeling and Analysis (CGCM3.2 T47), and the Center for Climate System Research at the University of Tokyo with the National Institute for Environmental Studies and Frontier Research Center for Global Change (MIROC 3.2) under A2 and B1 emission scenarios were compared to historical conditions. From the joint venture of the United States Bureau of Reclamation (USBR) and other research and university facilities, bias-corrected constructed dialogues (BCCA) daily downscaled precipitation and climate data was processed and used to drive the Watershed Analysis Risk Management Framework (WARMF) hydrologic model to simulate future changes in the UCRB. WARMF performs daily simulations of snow and soil hydrology to calculate surface runoff and groundwater accretion to river segments, lakes, and reservoirs. All model scenarios project a reduction in 21st century flows, though the magnitude varies with location and elevation. Results illustrate basin-wide temperature increases at low elevations, with extreme seasonality increasing at high elevation stations in future climate. Reservoir levels in Blue Mesa declined more than 70 per cent, but other reservoirs showed varying results dependent on location and climactic conditions. The resultant climate change scenarios will motivate adaptive watershed planning and management decisions and policies in response a changing climate and mitigate future concerns.