A new analysis is warning that water stored in the Colorado River’s two largest reservoirs — Lake Mead and Lake Powell — could fall to critically low levels in just one year if current water use continues and next winter and spring brings little relief.
The study, released on Thursday by water experts including Anne Castle, Senior Fellow at the Getches-Wilkinson Center for Natural Resources, Energy, and the Environment at the University of Colorado Boulder, paints a stark picture by the end of summer 2026, combined storage in Mead and Powell could shrink to just 9% of what they held at the start of the 21st century.
The report focuses on “realistically accessible” water — the supply stored above critical safety thresholds for dam operations. Right now, that buffer is about 6.3 million acre-feet, enough water to supply nearly 19 million homes for a year.
With water consumption across the basin outpacing natural inflows, the system is heading into a deficit. If next year’s inflows are similar to this year’s, and water use continues at recent averages, that cushion could be cut almost in half — down to 3.6 million acre-feet, or enough for about 11 million homes by late summer 2026.
Castle said the timing is critical because while negotiations over new river rules are underway, the immediate threat is that storage will drop in the next year.
“If we delay reducing water usage, we may find ourselves in a bigger hole at the beginning of the Post-2026 guidelines,” Castle and other coauthors said.
These numbers aren’t just benchmarks on paper. If reservoir levels sink below 3,500 feet at Powell or 1,000 feet at Mead, dam operations become compromised. That threatens power generation, water deliveries, and the overall stability of the system that serves 40 million people, dozens of tribes, and millions of acres of farmland.
The report urges immediate reductions in water use across both the Upper and Lower Colorado River Basins — rather than waiting for the new rules to take effect. Experts warn that another dry winter could accelerate the decline, leaving little margin for flexibility in 2026.
“We need a management plan for the basin overall that allocates how much water each state can use and then within the state we can figure out how that burden of reduced supply gets allocated,” Castle explained.
For communities across the Southwest, the message is clear: conservation can no longer wait.
