Mitigating the effects of climate change on the water resources of the Columbia River basin

Potential effects of climate change on the hydrology and water resources of the Columbia River Basin were evaluated using simulations from by the U.S. Department of Energy and National Center for Atmospheric Research Parallel Climate Model (DOE/NCAR PCM). This study focuses on the implications for the water resources of the Columbia River basin using climate projections for the 21st century based on a “business as usual” global emissions scenario, which we compared with a control climate scenario based on static 1995 emissions. Transient monthly temperature and precipitation changes were simulated through statistical downscaling of the PCM scenarios, which in turn were subsampled to produce daily forcings that drove a macro-scale hydrology model of the Columbia River basin at 1⁄4 degree spatial resolution. For a 20-year time slice (2040-2060) from each of three PCM transient ensemble members, an alternative dynamic downscaling was produced using a regional climate model (RCM). For the three PCM analysis periods used in this study, (2010-2039, 2040-2069, 2070-2098), changes in temperature averaged +0.5, +1.3, and +2.1 °C, respectively, and for precipitation changes in the critical winter season were small (-3, +5, and +1 percent), although they were somewhat larger in the summer. For RCM, the predicted temperature change for the 2040-2060 decades was +1.2 °C, and the average precipitation change was -3%. Due to the modest changes in winter precipitation, temperature changes dominated the simulated hydrologic effects by reducing winter snow accumulation, thus shifting summer and autumn streamflow to the winter. These hydrologic changes were reflected in simulations of the reservoir system by increased competition for regulated storage between firm hydropower and environmental