People are still using more water than the Colorado River Basin can supply, and it’s shrinking the water savings account for 40 million people, according to a new analysis from basin water experts.
The basin states, including Colorado, need to cut their uses now, the experts said
Water stored in Lake Mead and Lake Powell, the basin’s two largest reservoirs, could fall to less than 4 million acre-feet of available water if the river’s flows and water demands are repeated next year, according to a report released Thursday by a team of Colorado River water experts.
The two reservoirs have a combined capacity of 58.48 million acre-feet, about 92% of the reservoir storage capacity for the entire Colorado River Basin.
“If no immediate action is taken to reduce water use, our already-thin buffer of storage in Lake Powell and Lake Mead could drop to just 9% of the levels with which we started the 21st century,” the authors said in a joint statement Thursday.
The Colorado River Basin includes seven states, 30 tribal nations and two states in Mexico. It includes the western half of Colorado, but tunnels and diversions carry river’s water to farms, ranches, cities, environments and industries around the entire state.
The basin has experienced prolonged drought since 2000, one of its driest periods in a 1,200 year record. The U.S. Bureau of Reclamation, which manages federal water projects in the West, states and other water managers tried to adapt to the shrinking supply by forging new reservoir rules and agreements over the past two decades.
Still, the basin’s water storage dwindled. In 2021 and 2022, the water levels in Lake Powell, on the Utah-Arizona border, and Lake Mead, near Las Vegas, fell to historic lows.
The basin’s reservoirs act like savings accounts that help pace the flow of water from mountain snowpack to the Pacific Ocean so that water reaches homes and businesses when they are needed.
But the basin has been operating in the red for years: Water users consistently take more water than nature provides, according to the new report coauthored by Jack Schmidt, Anne Castle, John Fleck, Eric Kuhn, Kathryn Sorensen and Katherine Tara.
The basin currently has about 6.3 million acre-feet in accessible storage in Lakes Powell and Mead, the experts said. “Accessible storage” is the amount of water above 3,500 feet in elevation at Lake Powell and 1,000 feet at Lake Mead. Those water levels are critical to make sure the dams can operate reliably and safely, according to Reclamation.
“If we continue business as usual, we will deplete nearly half that amount,” the experts’ report said. They calculated basinwide overuse would be about 3.6 million acre-feet over the next 12 months if the river’s flows and water demands are the same as this year.
The results are grim, the experts said in the report.
“How close to the edge of the cliff are we?” they asked.
In this scenario, the basin won’t have very much flexibility in how it manages its water supply once new reservoir management rules go into effect in August 2026.
These rules, which will replace the current system established in 2007, are still being negotiated among states, tribes and the federal government. Who cuts back on water in dry years, and by how much, is one of the fundamental sticking points in the negotiations among the seven basin states.
Some water cuts are already happening. Under the current rules, Reclamation will cut the amount of water going to Arizona and Nevada by 533,000 acre-feet. It will also cut the water delivery to Mexico by 80,000 acre-feet. That’s the same reduction as in 2025.
One acre-foot of water, about 325,850 gallons, roughly equals the annual water use of two to three households.
On top of that, the federal bureau estimated that the Lower Basin will conserve an additional 800,000 acre-feet in 2026. Mexico will conserve an additional 67,000 acre-feet.
The experts are calling for more. The challenge, in part, is nature. There are more years, more frequently, with less water in the basin, but officials need to plan for that, the experts said.
“The entire basin is in agreement that we must balance our water use with the natural supply,” the report said. “Despite laudable efforts, we are currently not doing so.”