Why Western States Are Competing for Lake Powell Water: The Megadrought Explained
Persistent drought across the Colorado River basin has dropped Lake Powell to historic lows, forcing the seven basin states to renegotiate water shares that were set nearly a century ago.
- Lake Powell stores water for the upper basin states and helps regulate deliveries to the lower basin.
- A two-decade megadrought combined with overallocation has cut the reservoir to roughly one-quarter of capacity.
- California, Arizona, and Nevada must accept large cuts while upper basin states seek to protect their own supplies and hydropower.
- New operating rules and possible compact revisions will determine how shortages are shared through at least 2026.
Lake Powell is the second-largest reservoir in the United States, formed by Glen Canyon Dam on the Colorado River in northern Arizona and southern Utah. It was built to store water for the upper basin states of Colorado, Utah, Wyoming, and New Mexico and to ensure that the lower basin states of California, Arizona, and Nevada receive their legal shares even in dry years.
How the Colorado River Compact divides the water
The 1922 Colorado River Compact divided the river's average annual flow of roughly 15 million acre-feet equally between the upper and lower basins. Each basin received 7.5 million acre-feet, with an additional 1.5 million acre-feet promised to Mexico by later treaty. The compact did not account for the river's high natural variability or for the fact that actual long-term flow has averaged closer to 13-14 million acre-feet. Lake Powell and Lake Mead were later constructed to buffer that variability.
Why the megadrought has changed everything
Since 2000 the basin has experienced the driest 22-year period in at least 1,200 years. Runoff into Lake Powell has fallen sharply because of higher temperatures that increase evaporation and reduce snowpack. At the same time, total consumptive use by farms, cities, and industry has remained near or above the river's reduced supply. As a result, combined storage in Powell and Mead has dropped from nearly full in 1999 to roughly 25 percent in 2023. Powell itself fell below the minimum power pool elevation in 2022, threatening hydropower generation at Glen Canyon Dam.
Current negotiations and state positions
The Bureau of Reclamation has required the lower basin states to reduce use by 2-4 million acre-feet per year starting in 2023. California has offered to contribute cuts only if the reductions are shared proportionally among all users or if the federal government compensates for lost agricultural water. Arizona and Nevada have already accepted deeper percentage cuts because they hold junior rights. Upper basin states have resisted mandatory cuts to their own uses, arguing that their allocations have never been fully developed and that Lake Powell must be kept high enough to deliver water downstream and generate electricity.
The competition centers on whether future shortages will be absorbed mainly by the lower basin, whether the upper basin will also accept limits, and whether the 1922 compact itself will be amended. Proposals range from voluntary conservation payments to permanent retirement of some agricultural rights.
The outcome directly affects drinking water for 40 million people, irrigation for 5.5 million acres of farmland, and the operation of 12 major hydroelectric plants. Without agreed reductions, reservoirs could reach dead-pool levels within a few years, ending reliable deliveries and power production.
