Arizona water providers agree to voluntary CAP water cuts to preserve levels at Lake Mead

TUCSON — Two Tucson water utilities will take new voluntary reductions on their allotment of Colorado River water, part of a wider effort by federal water managers to shore up supplies in the drought-stricken system.

Tucson Mayor Regina Romero signed an agreement Wednesday with the Bureau of Reclamation to leave 110,000 acre-feet in Lake Mead over the next three years. Metropolitan Domestic Water Improvement District, or Metro Water, which serves over 50,000 people and hundreds of businesses in the Tucson area, signed a similar agreement for 15,000 acre-feet.

Tucson and Metro Water will take the reduction through 2025 and will be compensated with $400 per acre-foot. Tucson had already offered to leave 60,000 acre-feet in the system between 2022 and 2023. An acre-foot is a measurement used by water managers and is roughly enough to supply about three Southwest households for a year.

Romero said the agreement will help the city fund "critical infrastructure improvement that will keep our region's water safe and secure."

The money comes from the $4 billion in drought protection that Sen. Mark Kelly, D-Ariz., and Sen. Kyrsten Sinema, I-Ariz., helped secure in the Inflation Reduction Act last year.

There are six more agreements across Arizona, Bureau of Reclamation Deputy Commissioner Michael Brain said at the conference, most of them in the metro Phoenix area. The agency will also soon accept new proposals for projects to conserve water in the Lower Colorado River basin, with a goal of keeping more water at Lake Mead, the largest storage reservoir on the river.

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"Reclamation's top priority is putting the resources from the Inflation Reduction Act and the Bipartisan Infrastructure Law to work in communities and on projects with the greatest impact. We are committed to ensuring that these investments deliver meaningful results," said Brain, who oversees the agency’s media relations.

The two agreements signed on Wednesday are separate from the plan that Arizona, California and Nevada submitted to the Interior Department on Monday to save 3 million acre-feet of Colorado River water.

But they are "a core component of the Lower Basin proposal," said Patrick Dent, the Central Arizona Project's assistant general manager. Dent recognized the participation from Arizona and Indian tribes as "critical to propping up and preserving the system."

At the signing ceremony, Deputy Commissioner Michael Brain said that six more agreements were underway. Interior officials announced that the agency had completed deals with Phoenix (150,000 acre-feet over three years), Glendale (21,000 acre-feet), Peoria (19,400 acre-feet), Scottsdale (18,000 acre-feet), Gilbert (3,600 acre-feet) and the Asarco mining company (56,000 acre-feet.)

All agreements were pursued through the Central Arizona Project, or CAP, which delivers Colorado River water to roughly 6 million people in Maricopa, Pinal and Pima counties.

“The projects funded under the program will help increase water conservation, improve water efficiency, and prevent the System’s reservoirs from falling to critically low elevations, threatening water deliveries and hydropower production," said Reclamation Commissioner Camille Calimlim Touton.

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A 'hydrologic disconnect'

Metro Water had signed an agreement with Reclamation to cede 25% of its annual CAP water allocation in 2019.

The water utility was the first to use this type of compensatory "system conservation agreement" with the federal agency. Under the agreement, 40% of its yearly allocation will now stay in Lake Mead, General Manager Joe Olsen said.

"I think it was more of a trial run to make sure that it was viable and appropriate," Olsen told the Arizona Republic. "We were the only municipal and industrial provider to have that kind of agreement until last year."

Metro Water doesn't serve its custumers Colorado River water. Its main service area is 13 miles to the east from where CAP water is stored, in the Avra Valley well fields, and the utility relies on pumping groundwater from nearby wells. That has allowed it to store and recharge its CAP water allocation in Avra Valley and Pima County farmland, where the utility trades it for credits that offset pumping. But it has also lowered the water table of nearby wells.

"There is a hydrologic disconnect," Olsen said.

In partnership with Marana and Oro Valley, Metro Water is building infrastructure that will take CAP water to the service area. They've been planning it for nearly eight years, and completion is about two and a half years away, Olsen added. The compensation for leaving more water will help pay for this infrastructure.

Tucson Water is also taking bigger reductions on CAP allotments with this week's agreement, and committed to leave about 22% more water in Lake Mead than in the two previous years.

"What we are celebrating today is what proper water resource planning has done for Southern Arizona, particularly the city of Tucson," said Tucson Water director John Kmiec.

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Investments on water safety and quality

The conservation agreement won't hurt Tucson Water's supplies. Last year, through the conservation agreement, the utility left 25,000 acre-feet in the system.

"That was still part of our excess CAP water," said Kmiec. "The community is only using about 100,000 acre-feet a year. Our contract is 144,000 acre-feet a year. So we were still banking water."

The money received last year from leaving CAP water in Lake Mead helped the city design and construct a PFAS facility on Broadway Blvd, the Tucson Water director told The Republic. The water utility wants to treat a plume of toxic manufactured chemicals, perfluoroalkyl and polyfluoroalkyl substances, emanating from Tucson’s Davis-Monthan Air Force Base and could continue to contaminate nearby wells.

"Future funds from this agreement going forward will go to look at other water resilient, water resource management capital projects, as well as more conservation-related projects to save water," Kmiec said. Some funds might go to build additional projects that increase wastewater recharge.

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Clara Migoya covers environment issues for The Arizona Republic and azcentral. Send tips or questions to clara.migoya@arizonarepublic.com.

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This article originally appeared on Arizona Republic: Arizona water utilities take volunteer cut on CAP water allocations