Arizona limits construction in Phoenix after years of water overuse

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PHOENIX — Arizona will stop approving new developments that rely solely on groundwater in the Phoenix Metropolitan Area due to years of water overuse, drought, and climate change affecting water supplies.

The groundwater aquifers, currently serving 4.6 million people across metro Phoenix, are lagging behind growth on a trajectory that would run just short of projected needs in 100 years, according to a new state groundwater model released Thursday by Arizona Gov. Katie Hobbs. As a result, the state’s water agency will not approve new housing construction that rely on groundwater.

The model estimates future supply and demand for the Phoenix Active Management Area, a zone that includes most of the metro area, where the state’s groundwater law requires the Department of Water Resources to certify that new homes have a safe 100-year water supply before they can be built. Based on the new model, some potential developments would fail that test.

The change does not affect existing homeowners, and officials stressed that major cities including Phoenix have ample supplies and can continue to grow. Hobbs also noted that about 80,000 unbuilt lots already are approved and can go forward.

“If we do nothing, we would face a 4% shortfall in groundwater supply over the next 100 years,” Hobbs said.

In an effort to reverse that trend, she said $40 million in repurposed federal COVID-19 recovery funds will go toward a new ADWR-administered fund, the Arizona Water Resiliency Fund, to promote groundwater conservation and seek sustainable water supplies.

Still, she said, Arizona and the Phoenix area will continue to grow. Most cities have diverse water supplies with room to keep building. “We are not out of water and we will not be running out of water,” Hobbs said.

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Available groundwater already fully allocated

Arizona State University’s Kyl Center for Water Policy analyzed the new model and concluded that all of the physically available groundwater in the Phoenix Active Management Area is fully allocated. But most metro Phoenix cities use a mix of water sources, including renewable supplies from the Salt, Verde, and Colorado rivers, and have reduced their reliance on groundwater.

Most cities also have secured assured water supply designations from the state, which means they can show a 100-year water supply. That applies to 12 Phoenix-area cities, and to areas supplied by three other water utilities. Those cities are not affected by the halt to new subdivisions. Phoenix’s city water department issued a statement in response to the report noting that groundwater accounts for only about 2% of its annual use.

It means those cities have secure water sources enough to grow, said Sarah Porter, the Kyl Center’s director. The trouble spots are largely in high-growth areas on the edges, in Buckeye and Queen Creek, she said, and they already knew they lacked an assured groundwater source to continue their building booms apace.

One result of this reality could be that developers will now focus on the urban core, Porter said.

“One of the things this may do is make higher growth in older, established cities more attractive,” she said.

Ultimately, Porter said, a model that directs growth away from water-insecure areas and into water-secure areas is exactly why the state legislators passed the groundwater protection act in 1980.

“One of the things it’s designed to do is make sure we don’t have new housing growth without a secure water supply.”

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Drought could further strain water supplies

Asked about uncertainty on the Colorado River and the water it supplies to central Arizona, the governor said a deal that Arizona and neighboring states have proposed to cut back over the next three years should stabilize the river’s reservoirs in the short term. Pressed on what will happen if the river suffers a deepening drought, officials acknowledged it could affect future findings when they run the model again.

Arizona Department of Water Resources Director Tom Buschatzke said while the current model projects an eventual shortfall unless the state acts, it also shows that Arizona’s groundwater protection program has slowed depletion from decades past.

“It definitely shows that the groundwater supply program is working,” he said.

The 4% shortfall represents the draining of 39 million acre-feet from the ground, Buschatzke said. The $40 million conservation fund is a first step toward reducing that shortfall, one that the governor called a “down payment.”

In addition to developers still being free to plan new projects in cities such as Phoenix, Mesa, Tempe, and Glendale, Buschatzke said, those working in other areas may be able to build if they secure credits for water that the state has banked underground over the years.

The areas most likely to face obstacles are around the perimeter, he said, including Buckeye, the White Tank Mountain region, and the southeast Valley.