A water supply used for Arizona's suburban growth 'is gone,' one negotiator says

The likely impending cutback, if not disappearance, of a certain class of Central Arizona Project water supply is raising uncertainty about an agency’s ability to support future suburban development through recharge.

The water in question is called NIA water, and it has made up more than 20% of the CAP’s historic total supply. It was formerly called non-Indian agriculture water because it used to be delivered to farmers.

But as CAP water rights were gradually transferred from farmers, the NIA supplies found their way to cities, mines and other industries, tribes and other entities.

Now, that supply is in jeopardy as water negotiators for the seven Colorado River Basin states grapple over how to cut their water use to keep the declining river from ever drying up.

“That (NIA) water is gone,” Arizona Department of Water Resources Director Tom Buschatzke told a Colorado River conference in Boulder on Thursday.

He was looking ahead to how the basin states will carve up the river’s diminishing supplies for a new operating agreement.

That raises questions about how the Central Arizona Groundwater Replenishment District can meet future legal obligations to recharge renewable CAP water into aquifers to compensate for groundwater pumped for many suburban subdivisions in growing areas near Phoenix and Tucson and in Pinal County.

Under state law, developers of new subdivisions in those areas must prove they will have an assured, 100-year water supply for them to be built. If that supply is to be pumped groundwater, the replenishment district must find renewable water supplies such as CAP water to put back into the aquifer to compensate for what’s pumped. Until now, the district has always been able to find such replenishment supplies since it began operations in the middle 1990s.

A February 2024 document, outlining how the district plans to obtain renewable supplies for the period covering 2025 through 2044, shows a major reliance on NIA supplies to meet replenishment obligations. Showing where the supplies will come from is a key element of the district’s next plan of operations that would cover the same period. The plan must be submitted to the Arizona Department of Water Resources for approval.

But at this time, agency officials don’t have answers to questions about how cutbacks of the NIA supply could affect its future activities.

In fact, it’s not clear when the board will even vote on a proposed plan, CAP Board President Terry Goddard told the Arizona Daily Star on Friday.

Despite Buschatzke’s comment, Goddard said he’s not ready to completely write off hopes of getting NIA supplies in the event of future good water years.

But when asked how confident he is of finding replacement supplies if that becomes necessary, Goddard replied, “That’s the $64,000 question, and I can’t really give you a high degree of confidence. The nature of this particular situation is one of water scarcity. That’s behind our questions about this.”

While possible future replacement supplies clearly exist to meet the district’s recharge needs, “obviously, any dependable replacement supply is going to be a difficult to find,” he said.

The district recharges CAP supplies in Maricopa, Pima and Pinal counties for developments built in areas not served by a water utility such as Tucson Water or the city of Phoenix that have formal state designations of having an assured, 100-year water supply. In the Tucson area, developments supported by recharge by the district include Quail Creed east of Green Valley and Saddlebrooke and Saddlebrooke Ranch, lying just north of the Pima County line in southern Pinal County.

Developments served by this district tend to be in farther-flung suburban areas such as the unincorporated communities of Green Valley, Quail Creek and SaddleBrooke near Tucson, and fast-growing Phoenix-area suburbs including Buckeye and Queen Creek.

The likely disappearance of the NIA supplies came into public view on Thursday, at the annual Colorado River conference in Boulder, sponsored by the Getches-Wilkinson Center for Natural Resources and the Environment.

There, Arizona water chief Buschatke said the NIA water will go away, based on “the numbers we negotiated” among the three Lower Basin states to reduce river water use to wipe out a longstanding “structural deficit” between use and supplies. To eliminate that deficit, the three states — Arizona, California and Nevada — have already agreed to trim their river water use by 1.5 million acre-feet a year — about 20% of the Lower Basin’s annual river water supply.

On Friday, ADWR spokeswoman Shauna Evans said NIA water supplies would be eliminated starting in 2027 if the seven river basin states go along with that action when they conclude now-contentious negotiations over how to replace their current operating regime for the river. It expires at the end of 2026.

That supply would be part of 760,000 acre-feet of Arizona’s river water supplies that the state has agreed to give up as part of the Lower Basin agreement aimed at wiping out the river’s structural deficit.

As of now, which Arizona users will take how much of the remaining cuts, beyond the loss of NIA water, isn’t known. Arizona officials haven’t started a process to decide how the cuts should be apportioned, ADWR spokeswoman Evans said.

Buschatzke had been talking at the conference about how the NIA water has helped support several CAP-based water rights settlements with tribes approved since 1999 to help satisfy their legal claims to river water. Those include settlements with the Tohono O’odham Nation in Southern Arizona and the Gila River Indian Community in Sacaton in Central Arizona.

But, referring to a recently reached settlement between Arizona and the Navajo and Hopi tribes to obtain some river water rights, Buschatzke said, “It was a tough discussion with the Navajo and Hopi to say that (NIA) water is off the table. We did that to say it’s totally unreliable. It’s not there. There’s not enough water in the system anymore.”

Tribes indeed are among the biggest recipients of this water, controlling well over one-third of the total NIA water rights available. The Gila River Indian Community has about 120,000 acre-feet of NIA water, more than one-third of its total supply — giving it the largest such share of that water in Arizona.

Phoenix is next in line with nearly 38,000 acre-feet. The Tohono O’odham Nation has about 28,000 acre-feet of NIA water, roughly one-third of its total CAP supplies. But its water rights settlement requires the feds to upgrade that supply to a standard municipal CAP supply that’s more likely to survive any early cuts in river water supplies.

The Gila tribe is also supposed to have about 15,000 acre-feet of its NIA supply similarly upgraded.

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Tucson Water has no NIA water. Marana controls 515 acre-feet of it. Rosemont Copper and Resolution Copper Co. both have small supplies of NIA water to be used for their proposed mines in the Santa Rita Mountains and near Superior, respectively.

But few entities are more reliant on NIA water today than the Central Arizona Groundwater Replenishment District, which is part of the CAP’s governing agency.

Its share of NIA water is small compared to that of the Gila tribe. But of about 77,000 acre-feet of water it plans to use for replenishment from 2025-44, roughly half, or 38,870 acre-feet, would come from NIA water, says a report from the district.

The rest of its planned supplies are more reliable. They include other, non-NIA tribal waters and municipal and industrial CAP supplies that will last longer, if not indefinitely, during shortages. Another chunk of the water consists of completely reliable long-term storage credits, which represent CAP supplies that the agency has recharged into the aquifer to be used in times of shortages.

The district’s current array of replenishment supplies is “more than sufficient” to meet its legal obligations for the next 20 years when CAP isn’t in shortage, the district’s February 2024 document says.

Under the worst possible shortage envisioned by the Colorado River’s 2019 drought management plan, which is less restrictive than a post-2026 cutback plan will be, the district would still have enough supplies for replenishment.

But it would rely heavily on other supplies besides what’s shown in its planned replenishment supply portfolio, including some reserves it’s accumulated for times of shortage, the district document shows.

Under a shortage that’s deeper than the worst possible shortage envisioned by the 2019 drought plan, the district could still meet its replenishment requirements in the Phoenix area for some time, “but the severity and length of shortage” would determine how long its reserves would be relied on, the document said.

The post-2026 Colorado River operating guidelines could increase the scale of shortage reductions by an unknown amount, the district said.

Asked by the Star how the disappearance of NIA water would affect CAP’s ability to meet its replenishment obligation, agency spokeswoman DeEtte Person replied, “This issue is to be addressed in the CAGRD 2025 Plan of Operations.”

CAP Board President Goddard told the Star, “NIA is in jeopardy. I’m not willing to wipe it all away, but if there continues to be a shortage, it’s possible it will not be there at all. Hope springs eternal. If we have a good water year, some of it will come back.”

Board consideration of this issue “for sure won’t be there until August and I expect it to be later in the fall, due to the uncertainties,” said Goddard, a former state attorney general and Phoenix mayor.

Asked about possible replacement supplies, Goddard mentioned importing groundwater from the Harquahala Valley west of Phoenix, by putting it into the CAP canal to deliver it to the Phoenix, Tucson and Pinal County areas.

Or, the water district could buy water rights from farms or other parties controlling river water supplies for cities or farmland along the river — which are less likely to be cut than CAP supplies during shortages.

Or, it could build infrastructure to transfer Salt River Project water in the Phoenix area into the CAP canal for delivery to its customers, Goddard said. Yet another potential supply could come from the proposed raising of the Bartlett Dam on the Verde River north of Phoenix so it could store more water for growing cities to use, he said.

But many of these ideas face potential roadblocks, either bureaucratic, legal or financial. No outside supplies can, for instance, be put into the CAP canal until the federal Bureau of Reclamation that built the CAP agrees on standards for the quality of the water that would go into the canal, he said.

The Bartlett Dam elevation project is expected to cost about $1 billion and must be approved by Congress. Communities along the river have fiercely opposed past efforts to transfer water rights from there to growing cities.

While all these supplies could be obtained, none will be easy or cheap to get, Goddard said.

Overall, he said, “I don’t think there is an abundant supply of reliable water for replacement for the NIA water right now. I’m skeptical we can find a complete replacement for NIA water.”

Looking beyond the NIA water’s future, Goddard said he will personally make an effort to ensure that whatever settlement the seven river basin states reach will be fair to Arizona. The four Upper Basin states (Colorado, New Mexico, Utah and Wyoming) and have so far said all future cuts in river water use must be borne by the Lower Basin states — a position Goddard and other Arizona users say is totally untenable.

“Everyone has some cuts, but we’re adamant. You can’t just balance the books on the water users on CAP. If cuts to our system are in the 500-600-700,000-acre-foot range, we’ve got obligations to tribal and industrial users, obligations to the existing economy of central and southern Arizona,” Goddard said. “You simply can’t talk about cutting us that far.”