21st century U.S. climate in CMIP5 experiments and its impacts on water yield

Wednesday, 17 December 2014: 8:00 AM
Vinod Mahat, Colorado State University, Fort Collins, CO, United States, Jorge A Ramirez, Colorado State Univ, Fort Collins, CO, United States and Thomas C Brown, Rocky Mountain Research Station, U.S. Forest Service, Fort Collins, CO, United States
Downscaled projections by seven CMIP5 general circulation models (GCM), corresponding to four representative concentration pathways (RCP2.6, RCP 4.5, RCP6.0, and RCP8.5), were analyzed to determine projected future changes in the hydro-climatology of the contiguous United States. The calibrated Variable Infiltration Capacity (VIC) hydrologic model was driven by the 24 climate projections (downscaled to 1∕8° × 1∕8°) to simulate snow water equivalent (SWE) and water yield over the 21st century. Although the majority of the climate projections showed an increase in precipitation over much of U.S., some projections showed precipitation decreases in parts of the South, the Midwest, and the western U.S. in the 21st century. All scenarios showed an increase in temperature throughout the U.S., with higher increase occurring in the northern half of the U.S. More severe droughts in the 21st century than in the 20th century are projected for parts of the Midwest, the South and the western U.S. Although water supply is not projected to change much in the northern half of the U.S., because of the much warmer temperature and temporal shift in the peak snow accumulation, this region is projected to experience a shift in the seasonality of streamflow/water yield causing the winter flow to increase and the summer flow to decrease.