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Phoenix water experts speak during a Zoom regional report.

Regional Report: Balancing Arizona’s Water Supply and Demand

How to address future demands for Arizona’s water supply

Arizona leads the nation with its rigorous water conservation effort, but per-capita water use has been plateauing. Arizona will not be able to keep conserving at higher rates using our past methods.

The state and Greater Phoenix are in good position to operate for more than a decade, which makes this an ideal time to begin addressing issues that will arise in the future and ensure continued sustainability for generations to come.

Gammage & Burnham founding partner Grady Gammage provided a snapshot of Arizona’s water supply and the next steps of remaining proactive in the “Return to Watering the Sun Corridor” report, which he and other panelists discussed in a GPEC regional report.

“People will ask me, ‘Do we have enough water?’ And the answer to that is exactly the same as if I ask any of you, ‘Do you have enough money?’ It all depends,” Gammage said.

“That’s the answer. It all depends. It depends on what lifestyle you want to sustain. It depends on what do you want to leave for your children and grandchildren. It depends on how much more do you want to add to the people who can live in this place.”

Panelists included:

Return to Watering the Sun Corridor findings

Water management is tied to drought and planned growth, and Arizona has made conservation and reuse a top priority as we transform the region into an innovation-centered economy with long term water security. Usage is below 1957 levels even though the population is six times larger, and Greater Phoenix reuses 90% of effluent produced in the region.

In recent years, though, efficiency of water usage has been in decline.

The 2011 “Watering the Sun Corridor” report projected that it would be sustainable for the state to use 2.8 million acre-feet of water per year. In 2020, about 2.5 million acre-feet was used instead due to a decrease to the upper Gila and Colorado rivers and the U.S. Bureau Reclamation’s expected effects of climate change.

After a decade, the 2011 projection has shown to be overly optimistic. Upon review, Gammage’s report found that 1.87 million acre-feet of water per year is a better target for a sustainable water supply.

With the expectation of about 8.5 million people living in Greater Phoenix in 2050, Gammage said that if no changes were made to the system, there would be 10-15 years until the water usage is not sustainable for the state – and that’s not taking into account agriculture needs of the Sun Corridor, which is made up of Maricopa, Pinal and Pima counties.

“I don’t want you all to take that as gloom and doom. There are not very many cities in the west that could show 10 or 15 years worth of growth without doing anything.  But we need to be thinking about where we go,” Gammage said.

Conservation vs. efficiency

Conservation is necessary, but simply limiting water use often does not address the root of the problem.

“There are really good outcomes from conservation. But we need to make sure that we’re connecting up conservation measures that we believe in [and] that we’re willing to sacrifice for with the outcomes that we want,” Porter said. “If we don’t have plants and trees, we’ll have a much hotter city. And so conservation that gets rid of trees and even grass may not result in an outcome that we want.”

In fact, per-capita use decreased by more than 10 gallons per capita since 2005. Broader upgrades are needed for Arizona’s water system.

One such way is to create more storage, which could include increasing reservoir capacity on the Verde River and Bartlett Lake. The state could also make more use of the flood control space at the Roosevelt Dam and find more ways to reuse.

Importing water from remote Arizona basins or the main stem of the Colorado River is likely, Gammage said. Both could be done through the Central Arizona Project canal.

Ultimately, a goal is to find a way to desalt ocean water at an inexpensive cost.

“These projects, whether it’s desal or investment in raising the dam and increasing the size of Bartlett, they will take advanced investment and regional collaboration and bring them to fruition,” McJunkin said.

“We do have options. But as we’ve done in the past, we really need to work together and recognize that our desert location requires us to think about and invest in these issues years, even decades, before they become problems.”

Long-term investments

Water plans are rarely short-term investments and quick results. As early as 1903, SRP created a program in which farmers put up their land as collateral for a loan to build the Roosevelt Dam, which helped build a dependable water supply. Construction on the Central Arizona Project’s 336-mile system from the Colorado River to central and southern Arizona began in 1973, and the 1980 Groundwater Management Act established laws to protect groundwater and create preservation provisions. These have helped form a bastion for the region and driven the growth that is seen today.

“As we look to the future, we need to remember what it took to get us here and continue making those necessary investments in both water infrastructure and resources to facilitate growth on resilient water supplies,” McJunkin said. “We cannot rest on our laurels.”

Past generations were prepared for this. Between SRP, CAP and other sources, there is an underground water bank with about 10 years’ worth of demand to be used when needed.

“It’s like a savings account in the bank,” Gammage said. “You’re hoping to keep it to pass it on to future generations. But if you need to use it, it’s there.” 

Arizona is unique in that sense. Cities, especially in desert environments, do not have that sort of water supply.

“I don’t think there is another city in the arid West that could show you the kind of presentation we just showed you that has thought as seriously or as carefully about where the water to support their future growth is coming from,” Gammage said.

Just because Arizona has done well managing water supply for populations of years past doesn’t mean the same plan will continue to work as Greater Phoenix continues to grow.

“Half or more of the development that is expected in the coming decades will rely on this program of essentially a promise to go find the water and replenish so that we don’t develop by mining away groundwater supplies,” Porter said. “At this point, it’s not in a scary situation. We’re at a very good opportunity where we can address this potential vulnerability.”

Related: Get more Arizona water facts