Tucson offers to leave more CAP water in the Colorado River

Tucson Water is offering to leave "significant volumes" of its annual Central Arizona Project water supply in the Colorado River for the next three years in return for financial compensation from the federal government.

But its letter to the U.S. Bureau of Reclamation making that offer didn't propose a specific cut to the city's annual CAP allocation. Supplying 144,191 acre-feet a year to Tucson Water, CAP provides virtually all of the drinking water served to more than 730,000 utility customers. Tucson has enough left over from that supply after serving those customers to recharge nearly one-third of the water into the ground to store for future use. An acre-foot will supply up to four Tucson families with water for a year.

"We are letting the (bureau) know we are interested in discussions over a potentially significant contribution over the next several years," Tucson Water spokeswoman Natalie DeRoock said in an emailed response to a question from the Star about why the utility isn't disclosing a specific amount of water it's offering to leave. 

Since Tucson has one of the larger CAP contracts in the state, "we are offering an undetermined amount at this time because we may have the most flexibility" in supporting a statewide conservation program, added Tucson Water Director John Kmiec.

The uncertainty of Tucson Water's proposal is similar in some respects to how some other Arizona responded to the bureau's requests to leave water in the Colorado River starting next year. The bureau seeks this water as part of what it calls a "system conservation" program.

This request is one portion of the bureau's multi-pronged strategy for bolstering the river's imperiled reservoirs, Lakes Mead and Powell. The bureau wants to cut Colorado River water use by 2 million to 4 million acre-feet a year total across the seven river basin states. 

The bureau asked cities, farms and tribes in the river's basin states to offer to leave some water in the river in return for compensation, ranging from $330 an acre-foot for water left for a year to $400 an-acre foot for water left for three years. Arizona, California and Nevada are in the Lower Basin.

Hesitation, uncertainty

Officials of several other Arizona-based CAP users, including Oro Valley, told the Star they are hesitant to make specific commitments at this time to leave water. That's because of a very real possibility that next year, the bureau will decide to cut its annual release from Powell to Mead in 2023 from a planned 7 million acre-feet to as little as 5.5 million acre-feet.

Such a reduction would dramatically lower Mead's water level, and ultimately lead to still more drastic cuts in water deliveries to the Central Arizona Project and to other Lower Basin water users.

While Oro Valley declined to offer to leave any of its CAP supply in the river, officials in cities including Phoenix and Peoria along with Tucson have put conditions on their offers, to try to avoid losing what they think would be too much water should additional cuts prove necessary.

The bureau has made no decision about next year's release, although it has held out the possibility of reducing it to keep Lake Powell's water level from falling too low. It is considering cutbacks for next year as it works on an environmental review of its options for river management. A draft environmental report is due next spring, with a final report and decision likely by summer 2023.

But an analysis released this month by Arizona water officials concluded that a 5.5 million acre-foot release in 2023, followed by a 6.5 million acre-foot release in 2024, could drop Lake Mead's level to barely 960 feet by fall 2024 — down from 1,043 feet this week.

When the lake falls below 950 feet, Hoover Dam's turbines would no longer generate electricity for its eight million customers around the Southwest. Lake Mead also would then sit only 55 feet above "dead pool," at which no water could be extracted to be sent downstream to water users in Arizona, California and Mexico.

Lake Powell appears to face an equally dire if not a greater threat. The farther it drops below its minimum power production level of 3,490 feet, the harder it will be for water in the lake to pass through the dam and be delivered to Lake Mead and the Lower Basin.

'On the razor's edge'

The Phoenix Water Department has offered to leave 30,000 acre-feet in the river for 2023. But it will leave it in separate "chunks" over the course of a year rather than at once, said Cynthia Campbell, the city's water resource planning manager.

The Gila River Indian Community, holder of Arizona's largest CAP allocation of 311,000 acre-feet, has declined to say how much water it will leave behind. The Tohono O'odham Nation has offered to leave some of its CAP supply of 74,000 acre-feet in the river but declined to publicly disclose how much.

Oro Valley opted to take all of its CAP allocation of about 10,300 acre-feet, in part because of the uncertainty of how much water will be released to Lake Mead next year.

"If I was guaranteed that what we did would benefit the Lower Basin states, I might be inclined to do it," said Peter Abraham, Oro Valley's water utility director. "Without that guarantee, any amount of savings we might do for Lake Mead might not be realized."

The Gila River community also sees "a lack of clarity" about how the bureau's environmental report might affect it, said tribal attorney Jason Hauter.

"It’s difficult to provide a number until further discussions are had with Reclamation," Hauter said. 

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These users are "on the razor's edge" of being able to meet their obligations to deliver water to customers with the reservoirs so low, said Kathryn Sorensen, a research fellow at Arizona State University's Kyl Center for Water Policy. 

"The uncertainty is intolerable at this point. The cities can’t be in a position where they pledge water and then in three months, the bureau comes back and cuts a lot more," Sorensen said.

In his letter to the bureau last week, however, Tucson Water's Kmiec didn't mention concerns Reclamation could later cut more water deliveries as a reason for not offering a specific amount of water. In fact, city officials are interested in discussing with the bureau opportunities for additional CAP conservation, to be carried out under different parts of of the bureau's water conservation program, he said.

"We appreciate (the bureau's) efforts in this area, and we welcome constructive dialogue, to address the drought crisis with prompt and responsive actions and investments to ensure the entire Colorado River Basin can function and support all who rely on it," Kmiec wrote.

Tucson seeks federal commitment

Kmiec did condition Tucson's willingness to leave water in Lake Mead upon getting a federal commitment that whatever conservation the city does now will be given credit if the bureau hasto make more cuts.

"Our intention is to avoid paying a water resources penalty" for participating in the bureau’s voluntary program, Kmiec said.

It appears the bureau will want more cuts beyond what the states have already agreed to in the 2019 drought contingency plan, "and it does not appear likely that voluntary participation in the bureau’s programs will completely forestall the need for the bureau to make difficult decisions in allocating available water," Kmiec said.

The prospect of as little as 5.5 million acre-feet coming down the Colorado from Lake Powell next year was first publicly raised by Arizona Department of Water Resources and Central Arizona Project officials at a Nov. 4 meeting of a committee of water officials and experts. The committee was formed to advise Arizona on how to prepare for renegotiaton of an earlier set of federal guidelines to operate the river's reservoirs.

"We didn’t come up with 5.5 million acre-feet out of thin air," ADWR Director Tom Buschatzke said at the meeting. "This is something Reclamation has discussed with us."

Such a cut will happen if "we got to bad enough hydrology on the river this winter," he said.

Bureau officials have said that if runoff into Lake Powell is less than 50% of normal next winter and spring, "they will need to stabilize the system, and we should expect less than seven million acre-feet," Buschatzke said.

Bureau officials can't speculate now on the possibility of a less-than-normal release from Powell to Mead, said spokesman Doug Hendrix. But Interior Department officials will hold a public webinar to go into more depth about where it stands, Hendrix said.

Scottsdale Water has submitted a conditional proposal to leave water in the river "so that we can be a part of continued talks and part of the solution," said utility spokeswoman Valerie Schneider. Scottsdale has rights to 52,000 acre-feet — more than any Arizona city besides Tucson and Phoenix.

She did not specify how much water the utility proposes to leave, adding: "Ultimately, contribution numbers would be based on a number of factors — something we are not comfortable sharing at this time since the proposal is just the first step in the process."

But in the Tucson area, Marana and the private Vail Water Co. have opted to take their full CAP allocations next year. They have much smaller CAP supplies than Oro Valley — 2,236 acre-feet a year for Marana and 1,857 acre-feet for Vail.

Since Marana uses its entire CAP supply in its water system every year, "we will have to order the full allocation," Marana Water Director Jing Luo said. "Meanwhile, staff are working diligently on drought awareness and water conservation to improve long-term water efficiency and sustainability for our community and the region."

While Vail Water might leave water in the river in the future, "right now we want to see how it plays out," said Kip Volpe, the company's vice president. "We don't have a lot to leave on the river."

The company uses "quite a bit" of its CAP supply, and, "I don’t want to get caught short," Volpe said. 

Photos: Construction of Hoover Dam on the Colorado River in the 1930s