Lake Mead

The U.S. government released projections Wednesday that indicate an even more troubling outlook for a river that serves 40 million people in the American West.

Federal officials declared a first-ever water shortage for the lower Colorado River, triggering mandatory cutbacks for some users. Ongoing drought across the West, increased demand and the wide-reaching effects of climate change have steadily reduced water levels in the nation’s largest reservoirs. Usage restrictions will begin in January, and are expected to be felt most sharply by farmers in Arizona.

U.S. officials on Monday are expected to declare the first-ever water shortage from a river that serves 40 million people in the West, triggering cuts to some Arizona farmers next year amid a gripping drought.

The massive reservoir on the Colorado River hit a new historic low on July 24, dropping below 3,555.1 feet in elevation. The previous low was set in 2005. The last time the reservoir was this low was in 1969, when it first filled.

Emergency water releases from reservoirs upstream of Lake Powell are underway to preserve the nation’s second-largest reservoir’s ability to generate hydroelectric power.

The water levels behind the Colorado River’s biggest dams are fast-approaching or already at record lows. The historic 21-year megadrought that is squeezing some Western states’ water supplies will also likely start showing up in energy bills, because those dams can’t produce as much electricity.

Another dry year has left the waterway that supplies 40 million people in the Southwest parched. A prolonged 21-year warming and drying trend is pushing the nation’s two largest reservoirs to record lows. For the first time this summer, the federal government will declare a shortage.

Colorado River water managers could be pulled back to the negotiating table as soon as next year to keep its biggest reservoirs from declining further.

The Colorado River’s biggest reservoirs are likely to drop to historically low levels later this year, prompting mandatory conservation by some of the river’s heaviest users.

States in the Colorado River Basin are ready to begin negotiating policies to govern the critical Western water source.