Downtown Phoenix and surrounding suburbs at dusk — Arizona cities are pressing for answers about Colorado River water held in underground storage.
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A growing number of Phoenix-area municipal leaders say they are being left without the information they need about a reserve of Colorado River water stored underground for times of surface-water shortfall. The Arizona Water Banking Authority, established in 1996 to capture and hold excess Colorado River deliveries beneath the desert, faces questions from cities that paid to bank that water and planned on using it as a safety net when river flows fell short.
Those municipal concerns come as policymakers scramble to rewrite the rules that govern how Colorado River supplies are shared. The current regulatory framework is due to expire in 2026, and a federal draft aimed at setting new terms would impose steep reductions on deliveries to the Central Arizona Project, the 336-mile canal that brings Colorado River water to much of the Valley. The three Lower Basin states — Arizona, California and Nevada — have been negotiating with the Interior Department and are working on an alternative, voluntary plan to spread reductions and avoid the harsher mandatory cuts in the draft.
Warren Tenney, who directs the Arizona Municipal Water Users Association and represents 10 Valley cities that together account for more than half of Arizona’s population, said state statute requires the Water Bank to allocate stored credits when cutbacks occur. “There should be no question about this,” Tenney said, framing the availability of banked credits as the explicit reason the water was set aside. “This is the purpose of why the water was stored, so why is it even being questioned?”
Tenney and other municipal officials say the lack of clarity is making it difficult to plan for a drier future. “We don't know how deep those cuts are going to go moving forward,” he said. “But we better at least have certainty that the credits that were stored on our behalf and paid for by our taxpayers, that we can access those and utilize them.” Those comments reflect long-running requests from AMWUA and some member cities for information about how and when banked water could be recovered.
Officials and former officials who have worked on urban water management say the issue has simmered for years. Cynthia Campbell, who previously served as the city of Phoenix's water resources management adviser, recalled that cities began making “a bit of noise” about access and transparency as far back as 2017 or 2018. That early push, she said, stemmed from municipal responsibilities to ratepayers and the practical need to know how stored credits might be removed from the ground and distributed. “This all plays into a real frustration on the part of the cities who are trying to be diligent and trying to plan for eventualities,” Campbell said. “Because they have real customers to serve, and they just don't feel like they're getting the level of cooperation that they would like to get from The Bank.”
The Water Bank has scheduled a special meeting for Tuesday morning that is open to the public, and municipal leaders expect it to address at least some of their questions. AMWUA officials say they have sought more detailed guidance and responsiveness from the Water Bank for years and have been disappointed by what they describe as a reluctance to engage while broader interstate and federal negotiations remain underway. At the same time, the federal government and the seven basin states continue contentious talks over future sharing rules — a process that has raised the risk of protracted legal battles if agreement cannot be reached.
State negotiators have been active in Washington as they attempt to shape any settlement. Tom Buschatzke, Arizona’s lead negotiator on the river, has been working to persuade Interior Department officials to consider the three-state voluntary reduction proposal rather than the more severe cuts included in the federal draft. Municipal leaders say that outcome would help, but they emphasize that it would not eliminate the need for immediate, clear answers about how banked credits will be treated under any new regime.
For cities that have invested in the Arizona Water Banking Authority over decades, the central question is straightforward: when and how will the credits they stored be made available if surface deliveries fall short? That practical concern — anchored in a statute that AMWUA leaders say requires allocation — is driving the demand for transparency at a moment when the entire river system is being renegotiated. Tuesday’s public meeting is expected to be the next opportunity for municipal officials, Water Bank representatives and members of the public to press for specifics about the availability and retrieval of banked Colorado River water.
Ahead of the AWBA special meeting today, AMWUA published a blog underscoring persistent uncertainty among its cities, Tucson and other providers over whether stored credits will offset 2027 Colorado River cuts. Colorado River researcher Ed Millard noted the session will examine using aquifer water to firm up Central Arizona supplies should the CAP face curtailment under basic federal coordination.
State documents and AWBA planning materials show the Arizona Water Banking Authority has developed roughly 4.4 million acre‑feet of long‑term storage credits from past underground recharge — a reserve that includes about 613,846 acre‑feet held for interstate (Nevada) purposes and a large remainder intended to firm Arizona municipal and tribal supplies.
In testimony to the Arizona Legislature in March 2026 the AWBA said much of its portfolio was acquired with partners’ funds and that it currently holds roughly 2,000,000 acre‑feet of credits tied to CAP municipal and industrial subcontractors and about 250,000 acre‑feet reserved for the Mohave County Water Authority, while acknowledging it has no formal, detailed post‑2026 firming policy and that recoveries would depend on partner agreements, recovery wells and CAWCD canal exchanges.
Separately, lawmakers this year introduced measures (notably HB 2099 and SB 1201) that would prohibit municipal providers from earning new long‑term storage credits for Colorado River or CAP water during a federally declared Colorado River shortage, a legislative development that could further complicate how stored credits are treated during multi‑year cutbacks.