Local Opinion: Tucson will not be another Rio Verde, thanks to our water utility

By Juliet McKenna

Special to the Arizona Daily Star (Jan. 25, 2023)

Juliet McKenna is a hydrogeologist and water planning consultant in Tucson and a member of the City of Tucson’s Citizen Water Advisory Committee.

My neighbor recently moved to Tucson from the East Coast and has had a lot to learn about rattlesnakes, cacti, the monsoon, and other things that make southern Arizona unique. Increasingly, this learning curve also includes water security.

Last week, after the Rio Verde development in the Phoenix area made national news because Scottsdale cut off its water supply, he asked me if this could happen to us. His concern was that even though we had just gotten nearly two inches of rain in early January, he didn’t think it was going to be enough to “fill our aquifers” and that we could end up like Rio Verde.

He’s certainly correct about rainwater — for many decades now, local precipitation has not been sufficient to meet our water demands. And like Rio Verde, our neighborhood is on the margin of the Tucson basin and there is very little, if any, groundwater beneath our homes.

But there is a key difference between the residents of Tucson and Rio Verde: in Tucson, we are served by a water utility so as customers of Tucson Water, our water supply situation is much more secure.

State law requires utilities like Tucson Water to prove its water supply is physically available for 100 years and to replenish the groundwater pumped every year. As a result, Tucson Water has invested in a robust water portfolio and resilient infrastructure. The utility maintains hundreds of wells across the Tucson Basin and also has a contract for Colorado River water. Delivered through the 336-mile Central Arizona Project (CAP) aqueduct, our Colorado River water is recharged and stored in an underground aquifer in Avra Valley west of the Tucson Mountains. The utility pumps the water out and delivers it on demand across the basin to its customers.

However, there are challenges ahead. Groundwater levels are declining in some areas of the basin because there are loopholes that allow pumping without replenishment, including private wells, agriculture, and mining. Rio Verde was developed by one such loophole — a “wildcat subdivision” without a water utility and no long-term water supply. Unfortunately, this type of development can still legally occur outside the boundaries of a water utility service area, leading to regional groundwater level declines.

And even within our service area, our Colorado River supplies are also strained, which is a renewable water supply that has allowed Tucson to grow. Last year, in response to crisis conditions in the Colorado River basin, Tucson Water voluntarily took less CAP water while delivering the same amount to customers. In the future, with more severe Colorado River shortages, deeper mandatory cuts in CAP water deliveries are likely. Fortunately, for the past several years, Tucson Water has annually purchased and recharged more CAP water than it delivers to customers, resulting in a net increase in our “balance sheet” equal to several years of water deliveries.

Our quality of life and survival requires continued vigilance not only by the water utility, which has been planning for the future, but by all who live here. We need to optimize the use of our local water resources — including rainwater, stormwater runoff, and reclaimed water — and hold others accountable for cleaning up groundwater that has been contaminated. We need to maximize the amount of Colorado River water that we store locally in our basin while CAP water is available. We need to protect our limited supplies through aggressive water conservation by all water users. And we need to close the loopholes that are allowing our aquifers to be drained.

Decades of careful planning and investments in infrastructure and water supplies at Tucson Water have not only allowed Tucson to prosper, but also laid a solid foundation for our future. We are on the right track — it will be up to all of us to make sure we stay on it.