"Without major changes in current water-management practices, there’s more than a 50–50 chance that reservoirs along the Colorado River will dry up by mid-century, according to research in press in Water Resources Research. These reservoirs provide water to 3 million acres of farmland and about 30 million people in 7 states and northeastern Mexico.
As a 2007 report by the National Research Council noted, contemporary paleohistorical studies reveal wide fluctuations in Colorado River stream flows during the past 500 years; thus, water entitlements and compacts made during the 20th century—the wettest century in a millennium—are based on overly optimistic assumptions about long-term supplies. Furthermore, predictions from global climate models largely agree that human-induced climate change will diminish Colorado River runoff by 10–30%. With the river basin now entering its 10th consecutive year of drought, water levels at the region’s dozen-plus reservoirs have dropped to 59% of capacity, down from 95% in the late 1990s. Meanwhile, regional populations dependent on this water supply continue to grow; for example, Colorado’s and Arizona’s numbers have surged by 30% and 40%, respectively."