Drought prep

As the Colorado River reservoirs supplying a third Arizona's water supply have dropped perilously close to deadpool levels, Mesa water officials have consistently painted a rosy picture of the city’s planning, the relative health of the Salt River Project reservoirs and the years-worth of water banked by in underground aquifers.

But during unusually tough questioning in a March 2 study session, some Mesa City Council members questionned staff’s sunny outlook and requested more details about how it would respond to deep cuts.

“I think we need to be bluntly honest with our constituency about what our water situation is,” Councilman Scott Somers said.

Somers cited an internal letter issued in February by Warren Tenney, executive director of the Arizona Municipal Water Users Association, to AMWUA’s board of directors warning members that “under the best-case scenario,” Arizona cities should expect a 50% reduction in their Colorado River allocations starting in 2024.

With over half of Mesa’s water coming from the Colorado River, a 50% cut would mean the loss of a quarter of Mesa's water current portfolio next year. That's three times larger than the deepest cuts contained in the Drought Contingency Plan that the Lower Colorado Basin states have been operating under during the drought.

The water group's chief also cautioned that a total loss of Arizona’s Colorado River allocation in the near future is possible either from a reservoir system crash or the courts upholding California’s senior water rights that require Arizona to take all cuts before California.

Somers asked Water Services Director Chris Hassert if Mesa was ready to lose that much water.

Hassert replied that a 40% to 50% Colorado River water cut would be “severe,” but the city could handle it.

“We put together a month-by-month operational plan for 2024 to look at how we would get by with that reduced amount of Colorado River water,” Hassert said. “We fare pretty good.”

“In fact, we don’t need to even look at anything like (using) long term storage credits,” Hassert continued. 

“One of the bigger challenges is how we turn down the two treatment plants because you can’t take a treatment plant that’s treating 24 MGD (million gallons per day) and turn it down to one.”

Hassert talked at greater length about the most dire scenarios than he has at any time in the past year.

“If we get into the worst-case scenario where Lake Mead drops another 100 feet and we get to deadpool, then we’re getting into an area where we’re getting into Stage Two, Three, probably most likely Four of our water shortage plan,” Hassert said.

Stage Four of Mesa’s Water Shortage Management Plan calls for mandatory measures to “ensure the basic water needs for Mesa residents and businesses will be met.”

Suggested responses include a 25% surcharge on water use above a certain amount, a prohibition on winter lawns and limits on how often dealerships can wash their automobiles.

“Once we get into those really, really deeper cuts that hopefully we don’t get there, but if we do, now we’re gonna need cooperation from the community,” Hassert said.

If the Mesa’s spigot to the Colorado River is cut in half next year as Tenney warned, Hassert said Mesa would ramp up its groundwater use to its full allocation of 12,000 acre feet per year (1 AF is 325,851 gallons) from its usual 8,000 AF per year.

If there are deeper cuts than that, Hassert said, Mesa may need to escalate groundwater pumping and tap into its long-term storage credits to fill in the gap.

Mesa has banked almost six years’ worth of surplus water underground.

Hassert told the council “our wellfield is sufficient” to pump out the water needed to cover the loss of Colorado River water, but the city is currently in the process of drilling more wells.

He said the city is planning to drill about 12 more wells in the next six years, raising the number of municipal wells by a third.

Hassert’s assurances of ample groundwater were not entirely comforting to council members.

Somers worried that having to rely on stopgaps to meet current demands would “really impact our development and our growth potential.”

Councilwoman Jenn Duff interrogated the water director about the sustainability of groundwater.

She wondered whether the aquifer could become permanently depleted if all the communities in the region started pumping more groundwater at the same time.

Hassert and Water Resources Advisor Brian Draper tried to reassure Duff that it would take a long time to deplete the aquifer.

“We do get a bit of recharge from the frontal range, say the Superstitions, you have the Goldfield Mountains, Usery (Mountains),” Draper said. “You do get some recharge there every year when it rains.”

He also said the aquifer beneath Mesa is recharged by stormwater retention ponds, and the city can pump potable water back underground if necessary.

Draper said the city has been monitoring groundwater levels in Mesa, and in some places the aquifer has grown.

“Our strategy is always centered around pumping in a way that preserves the aquifer and doesn’t do any long term damage to the aquifer in terms of subsidence or drawing that down,” Hassert said.

In his remarks during the discussion, Mayor John Giles expressed a desire to firm up Mesa’s long-term solutions for a world where less Colorado River water is available.

Mesa has many ideas and plans in the works to get there, but they remain distant and uncertain.

“Part of this discussion reminds me of our plan to meet our climate action goals, which are … aspirational goals. We don’t know how we’re going to get there. It’s going to be new technology … I’m less comfortable with that being the plan for the water question,” Giles said.

“I can’t say to people, ‘25 years from now, we’re not going to have to just call a halt to development,’” Giles said. “That’s the doomsday scenario that we’re all planning for today.”

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