Researchers Say Climate Change Could Produce Water Crisis in Western U.S.

Observations throughout the western U.S. show snowpack is decreasing, rivers are flowing earlier in the year, and spring temperatures are increasing. A formal detection and attribution study of these changes shows the majority of these trends are due to human effects on the climate.

[Image courtesy of David W. Pierce, SIO; land image courtesy of NASA's Earth Observatory]

Researchers in a new Science article published online warn that human-caused climate change has dramatically altered the water flow over the past 50 years in several Western states.

These changes, which include more winter precipitation falling as rain instead of snow, an earlier snow melt, and new river patterns, combined with a general warming of the region, could cause a "crisis in water supply" for the Western United States, said the authors.

"Our results are not good news for those living in the western United States," wrote the researchers, led by Tim P. Barnett, a research marine geophysicist at the University of California, San Diego, adding that his findings make "modifications to the water infrastructure of the western U.S. a virtual necessity."

Due do the earlier snow melts, rivers will have a relative increase in water volume in the spring, and a relative decrease in the summer as climate warming continues, the authors wrote.

Barnett and colleagues' analysis of these new water flow models suggests that around 60 percent of the new patterns can be explained by climate change related to human-produced greenhouse gases and aerosols.

As water flow patterns change, the researchers say that states are going to have to change their storage capability to meet the changing river flow and shift their water resources from rural agriculture to urban centers.

This could have economic consequences, the authors suggest in study published 31 January on Science Express, the online site for the journal Science.

"Water is the most precious natural commodity in the Western United States," they wrote.

Becky Ham and Benjamin Somers

1 February 2008