Regional Report: Arizona’s Water Position

A review of Arizona and Greater Phoenix water as Colorado River cuts loom for the Lower Basin 

On Aug. 21, the Bureau of Reclamation announced its Colorado River post-2026 operations plans, outlining water cuts for the Lower Basin states of Arizona, California and Nevada.

Under the 10-year plan that will be reviewed and renegotiated every two years, Arizona will see a decrease of 760,000 acre-feet in 2027 and 2028, California will see a decrease of about 440,000, and Nevada will see a cut of 50,000. This total of 1.25 million acre-feet (MAF) will be in addition to a voluntary cut of an extra 700,000 acre-feet from these three states. The Upper Basin states of Colorado, New Mexico, Utah and Wyoming will not take any cuts at this time.

This announcement, called the Record of Decision (ROD), is less aggressive than the previous Environmental Impact Statement from the Bureau of Reclamation, which stipulated cuts of up to 3 MAF for the Lower Basin states. The ROD aligns more closely to an agreement between the three Lower Basin states established in May.

“As Colorado River availability decreases, we can backfill those supplies with groundwater, banked water and other sources,” said Kathryn Sorensen of the ASU Kyl Center for Water Policy.

Sorensen was one of three panelists on a Greater Phoenix Economic Council (GPEC) webinar in the days leading up to the release of the ROD. The group of local experts spoke about Arizona’s water position and how decades of water management have helped the state and Greater Phoenix prepare for Colorado River cuts.

The panelists were:

• Alexandra Arboleda, Partner at Gammage & Burnham and Central Arizona Water Conservation District Board Vice President
• Dr. Kathryn Sorensen, Director of Research at the ASU Kyl Center for Water Policy
• Dr. Max Wilson, Water Resource Management Advisor for the City of Phoenix
• Eric Sperling, CEO, Social Television Network (Moderator)

“Both of these things can be true: The Colorado River can be in crisis, and we can also be ready to withstand that crisis and protect our economies,” Sorensen said.

Watch the webinar here.

How did we get here?

There are a number of reasons the Colorado River, Lake Mead and Lake Powell are shrinking. It’s not necessarily an increase in water usage — Arizona uses about the same amount of water as it did in the 1950s, and less than it did in 1985 — but rather a 25-year drought and weather conditions that reduce runoff into the lakes and dams.

From 2020-2025, annual snowpack was around average, according to Arboleda. Central Arizona Project (CAP) data shows that three years had below-average snowpack, while three years had above-average snowpack.

However, runoff is consistently far lower than average. Only 2023 (161% of average snowpack) exceeded average runoff (140%). None of the other years exceeded 83% of the average runoff, and two years were below 50% of the average runoff. This means less precipitation made it into the rivers.

Percentage of annual average snowpack vs. runoff

Source: Central Arizona Project

The disparity between snowpack and runoff comes from a variety of factors, including hotter weather changing patterns of snowmelt and evaporation.

“That is one of the things that is most concerning to us looking forward as planners for the future,” Arboleda said. “If you get years where you have 92% of average snowpack and only 49% of average runoff, you’re going to get less water in the system.”

This has contributed to Lake Powell and Lake Mead having their lowest levels on record. The reservoirs in the Upper Basin 63% full on average, with several capturing 73%-96% of capacity.

“We believe, in Arizona, that the law is pretty clear that some of that water has to be released from the basin reservoirs to meet the delivery obligation to the Lower Basin,” Arboleda said. “We are advocating that the federal government needs to recognize that responsibility and release some of that water.”

Steps to ensure reliable water access in Arizona

Arizona has prepared for Colorado River shortages for decades. The state has established water banks and aquifers to store excess water for future use. Deep groundwater stores provide security for residents and businesses operating here.

In the short term, these water banks will offset shortfalls from Colorado River cuts.

Wilson disputed concerns that using these backups shows a lack of strategy on the part of the state or municipalities.

“We developed these backups for the purpose of being able to utilize them in times like this,” Wilson said. “We’re not going to feel bad about dipping into them in times like this when they’re needed to be able to maintain reliable water service moving forward.”

While these underground banks and aquifers will last a long time, they’re not infinite. Municipalities in Greater Phoenix are evaluating next-generation supplies including dam expansion, advanced water purification (AWP) and desalination.

Dam expansion is important to ensure that precipitation is not lost in wet years. In 2023, Bartlett Dam was not large enough to contain all the snowpack, forcing releases of water that could have otherwise been used to supplement shortages in future, drier years.

Phoenix is building three AWP facilities, with the Cave Creek Water Reclamation Facility expected to begin producing potable water in 2027. These facilities, which have been used around the world for decades, utilize processes like reverse osmosis, ultrafiltration through a membrane bioreactor, and ultraviolet oxidation to make reused water safe for consumption.

Desalination is a longer-term plan, though expenses to users would be “an order of magnitude” higher than water from the CAP, Sorensen warned, making it less practical than AWP and continued storage and conservation. Proposed water swaps with the San Diego County Water Authority are in play. San Diego operates the largest desalination facility in the country, which could allow excess Colorado River entitlement to be sold to Arizona providers.

These are forms of water management that continue a legacy of water stewardship in Arizona. From Indigenous and early settler canals to the 1980 Groundwater Management Act to shifts from a water-intensive agriculture economy to a more industrial-based one, the state has managed and maintained sustainable water use throughout its history. Now, it’s more important than ever to find new supplies to ensure continued reliability for all users.

“While drought management and demand management may be a short-term part of the solution, ultimately, this is not a demand problem that we’re facing. It’s a supply problem,” Wilson said. “It’s going to take supply solutions to address it.”