Submitted on November 2, 2007
Accepted on January 23, 2008
Human-Induced Changes in the Hydrology of the Western United States
Tim P. Barnett 1*, David W. Pierce 1, Hugo G. Hidalgo 1, Celine Bonfils 2, Benjamin D. Santer 2, Tapash Das 1, Govindasamy Bala 2, Andrew W. Wood 3, Toru Nozawa 4, Arthur A. Mirin 2, Daniel R. Cayan 1, Michael D. Dettinger 1
1 Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.
2 Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
3 Land Surface Hydrology Research Group, Civil and Environmental Engineering, University of Washington, Seattle, WA 98195, USA.
4 National Institute for Environmental Studies, 16-2, Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
* To whom correspondence should be addressed.
Tim P. Barnett , E-mail: tbarnett-ul{at}ucsd.edu
Observations have shown the hydrological cycle of the western U.S. changed significantly over the last half of the twentieth century. Here we present a regional, multivariable climate-change detection and attribution study, using a high-resolution hydrologic model forced by global climate models, focusing on the changes that have already affected this primarily arid region with a large and growing population. The results show up to 60% of the climate related trends of river flow, winter air temperature, and snow pack between 1950-1999 are human-induced. These results are robust to perturbation of study variates and methods. They portend, in conjunction with previous work, a coming crisis in water supply for the western United States.
