April 21, 2009

Climate change: Colorado river shortfalls?

U.S. scientists say currently scheduled water deliveries from the Colorado River are unlikely to be met if human-caused climate change reduces runoff.

The Colorado River system supplies water to tens of millions of people and millions of acres of farmland, and has never experienced a delivery shortage. But scientists at the Scripps Institution of Oceangraphy at the University of California-San Diego say if human-caused climate change continues to make the region drier, scheduled deliveries will be missed up to 90 percent of the time by the middle of this century.

All water-use planning is based on the idea that the next 100 years will be like the last 100, said Scripps marine physicist Tim Barnett, a co-author of the report. We considered the question: 'Can the river deliver water at the levels currently scheduled if the climate changes as we expect it to?' The answer is no.

Barnett and Scripps climate researcher David Pierce found reductions in the runoff that feeds the Colorado River mean it could short the Southwestern U.S. states of a half-billion cubic meters (400,000 acre feet) of water per year 40 percent of the time by 2025. By the later part of this century those numbers double.

The study appears in the Proceedings of the National Academy of Sciences.