Near-term acceleration of hydroclimatic change in the western U.S.
Article first published online: 1 OCT 2013
©2013. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Atmospheres
Volume 118, Issue 19, pages 10,676–10,693, 16 October 2013
How to Cite
2013), Near-term acceleration of hydroclimatic change in the western U.S., J. Geophys. Res. Atmos., 118, 10,676–10,693, doi:10.1002/jgrd.50816., , , , , , , and (
- Issue published online: 30 OCT 2013
- Article first published online: 1 OCT 2013
- Accepted manuscript online: 7 SEP 2013 04:20PM EST
- Manuscript Accepted: 5 SEP 2013
- Manuscript Revised: 3 SEP 2013
- Manuscript Received: 30 JAN 2013
- NSF. Grant Number: 0955283
- DOE awards. Grant Numbers: 3ERKP777, DE-FG02-08ER64649, DE-SC0001483
- ORNL LDRD award. Grant Number: 32112413
- near-term projections;
- hydrological change;
- western United States;
- snow cover;
- hydrological modeling
 Given its large population, vigorous and water-intensive agricultural industry, and important ecological resources, the western United States presents a valuable case study for examining potential near-term changes in regional hydroclimate. Using a high-resolution, hierarchical, five-member ensemble modeling experiment that includes a global climate model (Community Climate System Model), a regional climate model (RegCM), and a hydrological model (Variable Infiltration Capacity model), we find that increases in greenhouse forcing over the next three decades result in an acceleration of decreases in spring snowpack and a transition to a substantially more liquid-dominated water resources regime. These hydroclimatic changes are associated with increases in cold-season days above freezing and decreases in the cold-season snow-to-precipitation ratio. The changes in the temperature and precipitation regime in turn result in shifts toward earlier snowmelt, base flow, and runoff dates throughout the region, as well as reduced annual and warm-season snowmelt and runoff. The simulated hydrologic response is dominated by changes in temperature, with the ensemble members exhibiting varying trends in cold-season precipitation over the next three decades but consistent negative trends in cold-season freeze days, cold-season snow-to-precipitation ratio, and 1 April snow water equivalent. Given the observed impacts of recent trends in snowpack and snowmelt runoff, the projected acceleration of hydroclimatic change in the western U.S. has important implications for the availability of water for agriculture, hydropower, and human consumption, as well as for the risk of wildfire, forest die-off, and loss of riparian habitat.