Reclaimed Water A Potential Boon Under Drought Contingency Plan

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The looming water crisis along the Colorado River is creating a scenario where—if new sources of water are not utilized—the whole region may suffer drastic cutbacks. There is a possible future where cutbacks harm the overall economy and viability of a sustainable future for the population of the Southwest. Unfortunately, without prohibitively expensive water projects and agreements with external regions—or relying on expensive desalination, Arizona’s future may rely on reclaimed water (wastewater that has been treated and put to another purpose). However, in the long run this may prove beneficial.

Under the Drought Contingency Plan (more thoroughly discussed in a previous post), Arizona has made changes to the legal treatment of reclaimed water.  Previously, as a result of the Underground Water Storage Savings and Replenishment Act of 1994 (see A.R.S. §§ 45–801.01—898.0), water consumers drawing from groundwater could take water from the Central Arizona Project (CAP) and recharge it, to receive a groundwater credit. In essence, they could “store” water from the river by pumping it into the ground and gain the right to withdraw it from the ground later. This law allowed for discharge of CAP into constructed recharge with a 95% long-term storage credit: put in 1 gallon today, receive 0.95 gallons tomorrow. This 5% disparity was largely to accommodate the requirements of the Ground Water Management Act of 1980 (A.R.S. § 45-401), which mandates that specific regions of the state be at safe-yield of groundwater withdrawal by 2025. There are no consequences for failing to reach safe-yield—beyond unsustainably living in the most inhospitable region in the country—and this requirement is only for specific zones within the State. But nevertheless 70% of the population of the state are subject to this requirement, and generally they’ve worked towards the goal of putting in more water than they are taking out.

Under the legal regime prior to the DCP, reclaimed water only granted a 50% storage credit. Though current reclamation technology produces water that is in many ways cleaner than well water, it is generally considered unsavory for consumption by humans. It has many agricultural, industrial, and municipal uses, however. Further, Arizona’s standards for reclaimed water are extremely permissive towards its use in agriculture.

Given the above, it makes sense why CAP was granted a higher recharge credit compared to reclaimed water. In 1994, the CAP canal had just been finished and the Arizona Legislature wanted to incentivize the usage of Arizona’s entire allocation of Colorado River Water while also reducing our groundwater pumping. Reclaimed water was an afterthought. But now that cutbacks of our River allocation may be on the horizon, it has been given a second look.

Largely in response to Tucson’s approach to water management, the laws passed by Arizona under the DCP raise the 50% credit for reclaimed water to be on parity with River water recharge. Under both the current and previous legal framework, reclaimed water can only be recharged through already existing river networks. The Santa Cruz, for instance, is now flowing for a small portion of its original run through downtown Tucson for the first time in 70 years as a result of this recharge.

While the long-term costs of treating effluent to near-potability are potentially higher than the upfront costs of constructing a recharge basin, utilizing the natural river and stream system through “managed” recharge has other benefits that may offset this long-term cost. Consider all of the development which has occurred along the areas in Phoenix with flowing water, now imagine if Tucson could—through managed recharge—bring the Santa Cruz back to where it was a hundred years ago. Increased tourism and patronization of new businesses along this corridor could provide funding for the treatment required to enable it. Managed recharge is just as effective at replenishing the aquifers as constructed recharge and restores riparian habitats that had been long lost due to over-development.

The bitter truth is we may have no choice but to implement further reclaimed infrastructure. Let’s assume a worst-case scenario, it’s 2024, and Lake Mead is at 1,040 feet (at the time of this writing, Lake Mead is at 1,084 feet). Arizona has entered Tier 3 reductions and is now forced to cut back on river consumption significantly. Lack of snowpack driven by climate change has also substantially affected Arizona’s in-state water sources. In this scenario the pipes aren’t necessarily shut off, leaving farms and suburbs to evaporate, but it would incentivize water consumers to begin collecting on their accrued long-term storage credits by taking more from the ground. Considering the economic and population growth in the state since 1980, it’s plausible that consumers could burn through these credits rather quickly as the number of overall consumers has greatly increased. This would result in rapidly depleting aquifers. Presumably the state government would act before a humanitarian crisis emerged, but unless water from reclaimed sources is brought in to supplement supply, this scenario increases in plausibility.

As water is used and reclaimed, it stays within the same system whether municipal or agricultural, which overall would reduce our consumption of other sources of water. Treatment costs may increase, and some studies have shown that municipalities can’t charge as high a rate for reclaimed water due to its sullied perception. This could make agriculture cheaper, as there are fewer restrictions on utilizing treated effluent for farming purposes as there are for human consumption. Further, reclaimed water is already used to cool the Palo Verde Nuclear Generating Facility, and has potential use in cooling new solar power plants and other industrial uses. Almost 80% of Arizona’s water consumption is for non-municipal purposes and moving towards 100% reclaimed water use there would free up fresh water for municipal consumption. 

The changes under the DCP very smartly incentivize the use of reclaimed water recharge and our future in the region depends on mitigating our dependency on the River and the Ground for our water sources. Given the necessity of water to survive, it seems likely that not only will reclaimed recharge increase, but new “toilet to tap” systems will be installed in municipalities around Arizona. These come with added costs and potential litigation if consumers are uncomfortable with drinking treated water, even though most Arizonans accept the precarity of life here and understand that effluent can be made extremely potable. Even without going that far, under today’s legal regime—thanks to the DCP—we can move towards using treated effluent in agricultural, industrial, and recharge systems, which will be an added benefit to the long-term survivability here in the Sonoran Desert.