The Colorado River’s reservoirs have diminished to the point that significant cuts to the water supplied to the seven states that rely on it will be necessary next year, a federal official warned Tuesday.

Bureau of Reclamation Commissioner Camille Calimlim Touton told the Senate Energy and Natural Resources Committee maintaining “critical levels” at the largest reservoirs in the United States — Lake Mead and Lake Powell — will require large reductions in water deliveries.

“A warmer, drier West is what we are seeing today,” she said at a hearing. “And the challenges we are seeing today are unlike anything we have seen in our history.”

Colorado, New Mexico, Utah, Wyoming, Arizona, California, and Nevada all receive water from the Colorado River and next year will see a decrease of between 2 million and 4 million acre-feet of water due to the ongoing drought that has gripped most of the Western U.S. (An acre-foot is the amount of water needed to cover one acre of land in one-foot-deep water.) Current allotments of water from the Colorado range from 300,000 acre-feet for Nevada to 4.4 million acre-feet for California.

“What has been a slow-motion train wreck for 20 years is accelerating, and the moment of reckoning is near,” John Entsminger, general manager of the Southern Nevada Water Authority, told the Senate hearing. “We are 150 feet from 25 million Americans losing access to the Colorado River, and the rate of decline is accelerating.”

The West has been suffering through an acute drought since 2020, part of a megadrought that began in 2000. The last 20 years have been the driest two decades in the last 1,200 years. This year is so far the driest on record in California. Scientists attribute these conditions to climate change, which causes more water evaporation due to warmer temperatures.

“As a climate scientist, I’ve watched how climate change is making drought conditions increasingly worse — particularly in the western and central U.S.,” wrote Imtiaz Rangwala, research scientist in climate at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, in May.