New pipeline will let Arizona recover banked Colorado River water

• Arizona is tapping into a reserve of Colorado River water that was stored underground starting in the 1990s.
• A new 3.6-mile pipeline will move the stored groundwater to the Arizona Canal for use by Phoenix-area cities.
• The $25 million project is a partnership between Salt River Project, several cities, and the Salt River Pima-Maricopa Indian Community.

Arizona is unlocking an old stash of Colorado River water that its cities socked away before climate change and overuse drained the river of its former excess and cut into the state’s supply.

Salt River Project has cranked open a new, 3.6-mile Gilbert Road Pipeline that will help move groundwater from wells into the Arizona Canal and to Phoenix-area water utilities. That includes Colorado River water that the cities poured into the desert at the Granite Reef Underground Storage Project on the northern edge of Mesa starting in the mid-1990s, when the river could deliver more than Arizona needed.

Between Colorado River water and reclaimed wastewater, Phoenix, Mesa, Scottsdale, Tempe, Gilbert, Chandler and Tempe have stored more than 1 million acre-feet of water in the aquifer there in one of the state’s largest groundwater banks. That’s nearly a third of what the state once took from the river annually, in the years before megadrought imposed a steadily worsening austerity. Those cities now have a way to move their stored water. The 36-inch-wide pipe can deliver it to the canal that flows to city water treatment plants and then to customers.

Saving water for hard times is one step toward building climate resiliency. Another is building the waterworks that can deliver it.

“You’ve got to make sure you can get water to where they need it,” SRP general manager and CEO Jim Pratt said. In the cities’ case, that means sending it through the same canal that already delivers water from the Salt and Verde rivers to their treatment plants.

The cities are beginning to discuss when they’ll tap their stored water and in what quantities, Pratt said. Meantime, SRP can use its own wells to supplement its Salt and Verde supplies during dry years like this one. At its July 30 debut, the pipe dumped about 4,100 gallons per minute into the canal, but has capacity to supply 20,000 gallons a minute.

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Pipeline is a decade in the making

The Granite Reef Underground Storage Project is one in an array of central and southern Arizona basins in which partners working with Arizona Water Banking Authority have stored nearly 4 million acre-feet of water since 1996, well over half of what the state uses from all sources in a year. Each acre-foot contains about 326,000 gallons and could support three households for a year if applied solely to domestic uses, though much of the state’s water is also spread on farms.

Including construction of new wells, the pipeline project cost $25 million, according to SRP’s water construction and maintenance chief, Sharon Morris.

The pipeline represents the kind of partnership that it will take to get water where it’s needed in the future, Morris said, because moving water requires building across jurisdictions. In this case, SRP built five new wells and the pipe, which hangs under a new bridge that the Maricopa County Department of Transportation built across the Salt River and travels across an easement provided by the Salt River Pima-Maricopa Indian Community to the canal on its land just north of the Beeline Highway. SRP also leases Salt River Pima-Maricopa land for the groundwater storage area.

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Salt River Pima-Maricopa President Martin Harvier said the pipeline is the latest in a long series of developments that follow in his people’s centuries-long tradition of building canals to move water to where it’s needed in the Salt River Valley. Like those ancestral canal paths in which many of the area’s concrete conveyances still flow, this pipeline will help future Arizonans thrive, he said.

“Water is life, so helping put this system in, I know we’re providing life” for the people who come next, Harvier said.

The pipeline project took more than a decade to plan, permit and build, which Pratt said shows how critical it is to think ahead.

“You’re thinking decades over time,” Pratt said. “That’s what it takes to make water supply resilient.”

Brandon Loomis covers environmental and climate issues for The Arizona Republic and azcentral.com. Reach him at brandon.loomis@arizonarepublic.com.

Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. 

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