The Canadian National Post has some of the science about climate change NewMexiKen mentioned — “Scientists raise alarms about an impending water crisis in the West but governments have yet to heed the call.” Concerning the western U.S. the article tells us:
Phillip Mote, a climatologist at the University of Washington recently found snowpack levels in the western United States have dropped considerably in recent decades. That has led to predictions that, over the next 50 years, snowpacks in such regions as the Cascade Mountains in Washington could be reduced 60%, cutting summertime stream flows as much as 50%. Those forecasts match the findings of Daniel Cayan, climate researcher at the Scripps Institute of Oceanography in La Jolla, Calif., who recently reported in the journal Climate Change that snowmelt in California’s Sierra Nevada now comes three weeks earlier than it did in 1948. “Snow is our water storage in the west,” Dr. Mote recently commented in the U.S. journal Science, “when you remove that much storage, there is simply no way to make up for it.”
Meagre snowfalls in the western U.S. last winter have resulted in projections suggesting snowmelt runoff into the Colorado River — the main water artery for Denver and Los Angeles as well as huge expanses of agriculture — could be 45% below average this year. The United States Geological Survey says the period since 1999 has been the driest in the 98 years of recorded history of the Colorado River.
The relatively humid 20th century is being shown to be an anomaly.