City of Phoenix braces for Colorado River cuts, plans to tap reserves

PHOENIX — The city of Phoenix says it is not running out of water but will need to tap into backup supplies to meet demand over the next 10 years.

The Phoenix City Council held a policy session on April 28 where the Water Services Department gave a presentation detailing how potential Colorado River water cuts would impact the city’s water management.

Phoenix’s five-point backup plan for potential cuts

As the city waits for final cut details, they’re adopting a plan to prepare expected Colorado River water cuts that includes water conservation campaigns and updated watering techniques for the desert.

The city adopted the following:

• An ad hoc water conservation committee adopted a number of projects including efficiency consultations, incentives for residential and commercial grass removal and rebates for high efficiency toilets and irrigation controllers.
• Phoenix invested in renewable surface water supplies like infrastructure on the Verde and Salt rivers to capture flood waters for storage so it can be used later.
• Expanded underground storage for unused water supplies.
• A $300 million drought pipeline project that allows the city to move water from the 24th Street Water Treatment Plant into Phoenix and the addition of more groundwater wells.
• Phoenix departments are developing specific drought management plans to conserve water while maintaining the services they provide to the public.

“To date we have 675,000 acre-feet of water stored underground, which equates to approximately four years’ worth of water supply currently used by our customers that primarily use Colorado River supplies,” said Director of the Water Services Department Brandy Kelso.

How Phoenix plans to make up the difference

Kelso walked the council through a tiered approach, starting with the renewable backup supplies outlined in step two of the city’s preparation plan, including water that would be captured behind a new gate system at Horseshoe Reservoir on the Verde River.

“You can see that we can fill the gap at a 25% cut and we barely are making ends meet on a 50% cut,” Kelso said.

Stored groundwater that Phoenix has been banking underground can then be layered in to meet a 50% cut, though the city would still fall a little short at 75%.

Natural groundwater allocations can also be tapped to help meet demand.

This resource is used last because it’s not renewable.

“Once it’s used, it’s gone,” Kelso warned. “Use of this supply will allow us to meet the 75% cut, but we as you can see are not able to make the 100% cut,” Kelso said**, referring to what the city has previously called its “black swan” scenario.

Phoenix entered a stage 1 water alert in June 2022, and Kelso expects the city to go to a Stage 2 water warning by the end of 2026, as the city begins drawing on backup supplies in early 2027.

“We are currently working on the aspects of what a Stage 2 water warning will look like. It may include things like additional conservation education, expansion of water audits, incentives and rebates to ensure efficient use of water,” Kelso said.

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