By Austin Corona/AZ Central
Two of Arizona’s largest pieces of water infrastructure are linking up.
A coalition of 14 central Arizona municipalities and water companies is working to complete the interconnection between the Central Arizona Project and the Salt River Project, two water systems that collectively serve more than 80% of Arizona’s population. While water can flow from one to the other, the new project would make transfers available in both directions.
Local governments say the new project will make them better equipped to handle a less predictable water future as the Colorado River suffers the effects of climate change and overuse. It is the largest of several projects that received federal funding this month.
The project, which partners began exploring in 2022, received $154 million in federal grant money on Jan. 15, approved through the Inflation Reduction Act. Stakeholders will cover the rest of the projected $247 million cost.
“(It is) essential that we create opportunities to capture excess water during wet periods, and put it to use across central Arizona. To get the most out of every single drop of this precious resource,” said Rep. Greg Stanton, D-Ariz in a statement on Jan. 15.
Stanton said he had pushed federal officials to fund the project, saying it was a “perfect candidate” for drought resiliency funds under the IRA.
The project will fully connect central Arizona’s massive and complex system of dams, canals, and underground water storage. While the administration of the two projects and their associated water supplies will remain separate, the physical infrastructure will link so that users can get water from either project transferred to them through the other, with some legal limitations.
“It will create flexibility and efficiency in the future, which is going to be important as the valley continues to grow and we have more and more concern regarding climate change and climate variability,” said Jacob Rodriguez, a senior manager of water system projects at the Salt River Project.
How a pipe and pump will connect CAP, SRP canals
The CAP and SRP both deliver river water to Arizona’s largest urban centers, as well as some farms. The CAP brings water to central Arizona from the Colorado River, while SRP brings water from the Salt and Verde watersheds, northeast of the Phoenix area. Together, they represent billions of dollars in federal investment and serve more than 6 million people.
An connection to move water from the CAP to SRP was built in 1990, but transferring water in the other direction is not possible. The new interconnection — a pipe and a pump connecting the CAP canal with SRP’s south canal north of Mesa (near the Granite Reef dam) — will allow water to move in both directions between the two systems.
In exchange for federal funds, SRP could leave an average of 1,000 acre-feet of water in Lake Mead each year over the next 50 years, though the number is up for negotiation. The lake, which lies on the overburdened Colorado River, dropped to record low levels in 2022 before states and the federal government acted to conserve water and prop up the reservoir.
SRP’s contribution would be practically negligible for the reservoir and a tiny portion of the total water Arizonans have conserved in the Colorado. In 2023, Arizona farmers conserved over 1.2 million acre-feet of water in Lake Mead, more than SRP’s entire average annual water delivery (around 1 million acre-feet).
While the project may not mean much to the Colorado River, it could make central Arizona communities better prepared as climate change and fierce competition make the Colorado less reliable. As Colorado River water becomes more scarce, the interconnection will give communities more access to stored groundwater under the SRP system and new water storage at a planned expansion of the Bartlett Dam on the Verde River.
A 'big deal' for Queen Creek
Paul Gardner, director of water resources for Queen Creek, said his town will probably lose access to the vast majority of its 4,495 acre-feet of Colorado River water after states and federal officials negotiate new water cuts in 2026.
“It is gone in our lifetimes unless the dams fill up completely,” Gardner said.
Queen Creek, historically reliant on groundwater, is struggling to build more surface water supplies into its portfolio after Gov. Katie Hobbs announced in 2023 that Arizona Department of Water Resources would not issue certificates of assured water supply to developments solely reliant on groundwater. The town has grown rapidly in the last 50 years through the unsustainable pumping of finite aquifers.
Queen Creek is technically “off-project,” meaning it doesn’t have access to SRP canals. With the interconnection, Queen Creek can receive water from Bartlett, an SRP reservoir, through the CAP, helping to fill the hole left by dwindling Colorado River supplies. New water behind the Bartlett expansion is not exclusive to SRP customers, and Queen Creek has a stake in the expansion project.
“It's a big deal for us,” Gardner said. “It's going to end up being 25-30% of our renewable water supply portfolio in the future.”
The project, the dam expansion, and a range of new aquifer recharge projects in central Arizona communities are all part of a larger effort to capture floods during wet years and stretch out the supplies in dry times — particularly important as Colorado River water becomes less dependable.
Capturing surplus water in wet years
Water managers hope the projects will help them avoid a repeat of surplus water releases from SRP reservoirs in 2023, when high flows from a wet winter forced dam operators to spill excess water down the river without capturing it for use.
"If this project had been in place in 2023, there would have been more than enough capacity to move 50,000 acre-feet of water from SRP during the high-water period we experienced that spring to water treatment plants or underground storage facilities along the CAP system . . . instead of that water being spilled downstream," Stanton said in his statement.
Queen Creek is busy expanding its capacity to use the kind of underground storage facilities Stanton referenced. The Bartlett expansion will help catch more of that water, and the the town believes it will receive an average of 10,000 acre-feet of additional water each year because of the interconnection. The dam will help catch more of that water, and the new interconnection will divert the excess to communities like Queen Creek, who are building access to more underground water storage so they can receive and hold on to that water for dry years in the future.
“You just need to really catch it, contain it, store it and recover it later,” Gardner said.
Queen Creek is planning to build two facilities for storing water underground. Gilbert, which also received grant money through the IRA, is also expanding its underground storage abilities at the Riparian Preserve at Water Ranch. Later on, the towns intend to recover that water by pumping it out of the ground.
“We're going to have to have increased pumping due to Colorado River shortages,” said Lauren Hixson, water resources manager for Gilbert.
Gilbert residents are getting a new tool to track their water use and save on their bills, thanks to the same round of federal grants funding part of the SRP-CAP interconnection.
The town is connecting all its residents and businesses’ water meters to a real-time database, meaning Gilbert and water customers can watch their water use on an hourly basis and figure out how to save on their bills.
Tracking leaks, saving money
The new system is meant to help Gilbert residents quickly catch leaks in their system. Hixson said the most common leaks happen in pool valves and outdoor irrigation systems. In the past, the town only collected monthly water use data, meaning a resident might not see a costly leak until long after it's started.
“This will be much more preemptive and more real-time, so people can make decisions a couple days or a couple weeks after the leak may have started, and then not get that bill after they've had a leak going for several weeks or several months,” Hixson said.
Gilbert residents might appreciate savings on their water bills now more than ever. Shortages on the Colorado River, along with inflation and water quality projects, have pushed Gilbert to raise its water rates — an average resident’s annual bill payments are expected to rise by $550 between 2024 and 2026.
The town has already integrated 30,000 meters into the system, with over 60,000 to go. The project will receive $3 million in federal funds.
Along with the meters, Gilbert will also use $14 million in IRA grants to increase its aquifer recharge capacity the Riparian Preserve at Water Ranch.
In exchange for the grant money, the Gilbert will leave 8,500 acre-feet of water in Lake Mead over the next ten years, enough to supply almost 1,800 average Gilbert households for that time period.
Sens. Ruben Gallego and Mark Kelly, both D-Ariz., released a statement celebrating the funds on Jan. 22.
"Securing Arizona's water future requires forward-thinking solutions, and these projects are examples of that,” Kelly said in the statement.
The grants will also fund a new wastewater reuse facility in Tucson.