Colorado River reservoirs hit historic lows as federal plan to cut water use is finalized

Three states ordered to cut 1.25 million acre-feet of water yearly

Lake Mead, the largest reservoir in the United States, has fallen to its lowest level since it was filled nearly 90 years ago. Upstream, Lake Powell is also at a historic low. The two reservoirs, which together anchor water deliveries to more than 40 million people across seven states, have a combined storage at its lowest level since before Lake Powell began filling in the 1960s.

Federal officials have responded by finalizing a plan requiring the three “lower basin” states — Arizona, Nevada, and California — to reduce their combined Colorado River water use by about 1.25 million acre-feet per year, with the major reductions taking effect in 2027 and the possibility of substantially deeper cuts later. The plan follows years of failed negotiations among the seven states to reach agreement on how they would use less water.

The Colorado River begins in small streams in the Rocky Mountains fed mainly by melting snowpack. It supplies water to more than 40 million people in seven states and irrigates more than 5 million acres of farmland. Hydroelectric dams on the river, including Hoover Dam on Lake Mead and Glen Canyon Dam on Lake Powell, generate electricity for communities across the Southwest.

“That’s what makes this so scary,” said Kyle Roerink, a senior adviser with the Great Basin Water Network. He said the West has spent decades using more water than the river can reliably provide.

“If it’s not a crisis, it’s crisis-adjacent,” Colby Pellegrino of the Southern Nevada Water Authority said of conditions on the river.

The white “bathtub ring” of mineral deposits left behind from when Lake Mead was last full, in 2000, now rises 175 feet above the current water level. The winter of 2025 to 2026 produced record low snowpack in the Rockies, leaving less water in the mountains to feed the river during the summer. Climate Central, an independent group of climate scientists and communicators, reports that extreme heat since 2000 has become a major driver of the drought: hotter conditions dry out soils and plants, so when precipitation arrives, more of it is absorbed by the landscape or evaporates before reaching streams and rivers.

The Colorado River has lost 20% of its flow during a 26-year megadrought that began in 2000, according to Kyle Roerink, a senior adviser with the Great Basin Water Network.

“Think of them as a bank account,” Roerink said of the two reservoirs. “When you see the bathtub ring and exposed shorelines you need to think, are we going bankrupt?”

Las Vegas, which draws more than 90% of its water supply from Lake Mead, has positioned itself as a model for conservation. The city treats and recycles nearly every drop that goes down a drain. As lake levels began falling in the early 2000s, the Southern Nevada Water Authority spent $1.3 billion to build a new intake nearly 200 feet deeper in the reservoir, along with a new low-lake-level pumping station. The “third intake” now allows southern Nevada to keep tapping the reservoir as water levels drop. A 1970-era intake that once drew municipal water from the lake can no longer operate because the water has dropped below it.

“I think it says that somebody had the climate projections right,” Pellegrino said.

Phoenix draws about 40% of its water from the Colorado River, and in some parts of its metropolitan area, home to more than 5 million people, the share approaches 100%. The water arrives through the Central Arizona Project, a 330-mile canal system that crosses the desert. Federal cuts are expected to reduce flow through the canal by roughly half next year, according to Max Wilson, the water resources management adviser for the City of Phoenix.

“This is the water that has enabled us to be able to settle the western United States and be able to settle here in central and southern Arizona,” Wilson said.

On a construction site at the city’s northern edge, workers are building an advanced water purification facility that uses reverse osmosis and ultraviolet light to clean already-used water to drinking-water standards. The plant is expected to produce nearly 7 million gallons of recycled water per day when it opens next year. Phoenix plans to build three of these facilities as part of a broader effort to reduce its dependence on the river.

“It’s one piece of the pie as we’re trying to figure out how to live with less Colorado River water,” Wilson said. “But it’s an important piece of the pie because it’s so reliable.”

The financial cost of adaptation is mounting. “We are going to be able to weather the storm but it’s going to be very expensive,” Roerink said.

Arizona, which has the most junior water rights on the river, is expected to absorb the largest share of the cuts. The four upper basin states — Colorado, Utah, Wyoming, and New Mexico — do not face mandatory cuts under the initial plan, a structure that has further inflamed tensions among the river’s users. Nevada is suing the federal government over the plan. Arizona is threatening to do so. California has argued that the long-term solution must involve all seven states. The dispute could eventually reach the Supreme Court.