The uncertainty surrounding the Colorado River

Last week, the U.S. Bureau of Reclamation released its closely watched August 24-Month Study , which sets the shortage status of the Colorado River’s major reservoirs, including Lake Mead—a lifeline for the Lower Basin states of Arizona, California, and Nevada. This year’s findings came as no surprise, and the current Tier 1 Shortage condition will extend one more year. The real challenge still remains. At the end of 2026, the operating guidelines for the entire Colorado River Basin will expire. The seven Colorado River Basin States have yet to agree on new rules for sharing the river’s water, despite worsening conditions on the river that clearly demand action.  

While we know our state will receive less Colorado River water  after 2026, the exact reductions remain unknown. This lingering uncertainty is particularly daunting for municipal utilities to prepare their water systems and help residents understand the challenges ahead. Under the plan advocated by the Lower Basin States , the AMWUA cities and other providers who receive their Colorado River from the Central Arizona Project (CAP) could receive at least a 20% reduction, a more severe impact than the worst shortage under the current operating guidelines. And that may be the best-case scenario.  

Planning for an unpredictable future means municipal providers are looking for ways to strengthen their communities’ water portfolios through diversified supplies, significant infrastructure investments, and expanded conservation programs.

Behind this urgency is the new reality – the Colorado River is not producing the water it once did due to overallocation, a 25-year drought that is the worst the region has experienced in centuries, and increasingly hot and dry conditions. The effects of aridification, including higher temperatures, dry soils, and earlier melt, result in less water reaching the river. Its impact is evident this water year. Snowpack upstream of Lake Powell peaked at 92% of the 30-year median, but inflow into Lake Powell is currently only at 50% of the 30-year average.

This hydrology tells a stark story. In just one year, the total storage capability of the entire system has decreased from 25.87 million acre-feet a year ago to 22.72 million acre-feet. The absent 3.15 million-acre feet is equivalent to eight years of Colorado River water deliveries to the AMWUA cities, based on 2024 volumes. The Basin’s two largest reservoirs, Lake Mead and Lake Powell, are each less than 32% full. These levels are well below what’s considered healthy for the system and signal serious challenges ahead for water supply, hydropower, and river health. Yet things could be much more dire if the Lower Basin States had not agreed to leave water in Lake Mead in recent years. This year, Arizona alone will leave over 850,000 acre-feet of water through a combination of mandatory Tier 1 shortage cuts that have heavily hit Pinal County farmers and voluntary contributions from tribes, the AMWUA cities, and others.

While the deteriorating conditions and health of the Colorado River are cause for concern, it is more alarming that the Upper and Lower Basin States have not yet reached an agreement for protecting a water supply for 40 million people. The Lower Basin States continue to propose creative concepts that would require all seven Basin States to live with less water to protect the critical infrastructure throughout the system and ensure the Colorado River can benefit all users in the Basin. Failure to reach an agreement could lead to years of litigation, strained interstate relations, and increased risks to municipal water supplies, tribal water, and agriculture, as well as to critical hydropower generation at Hoover and Glen Canyon Dams—all of which would negatively impact the U.S. economy. 

Realistically, those who rely on this vital water source know they cannot control Mother Nature’s impact on the Colorado River but need to efficiently and effectively manage the water that the river does supply. That’s why the AMWUA cities have been actively planning for a future with less water and will continue to do so despite not knowing the extent of the reductions they’ll face in just 16 months. 

For 56 years, the Arizona Municipal Water Users Association has worked to protect our member cities' ability to provide assured, safe, and sustainable water supplies to their communities. For more water information, visit www.amwua.org