Water in crisis: despite conservation efforts, Arizona’s groundwater supply still at risk

by KATHERINE SYPHER | July 8, 2021

Editor’s note: This article is part of a collaboration between APM Research Lab and the Ten Across initiative, housed at Arizona State University.

According to a new report out of Arizona State University, water conservation in the state hasn’t gone far enough in protecting groundwater. Considering this warning and the on-going droughts and wildfires currently threatening much of the nation’s Southwest, APM Research Lab thought it worthwhile to look at the backstory of groundwater use in one of the nation’s driest and most rapidly growing states.

The story of water in the southwestern United States is increasingly one of scarcity. Millions of people live in the region’s naturally arid environments and populations are growing rapidly. States and cities have improved their water efficiency and conservation in recent years, but during ongoing stretches of low precipitation and drought, many are still using more water than the environment can sustain. 

One important source of water are aquifers—underground bodies of porous rock that hold water— and some are in trouble. Across the country, aquifers face the risk of pollution, being inundated with salt water and being depleted altogether. This is troubling because water in these aquifers is largely considered a nonrenewable resource—once they are empty or contaminated, they can be extremely difficult or impossible to restore.  

Tucson, Arizona is among the nation’s metro areas that are particularly focused on groundwater. This is in large part due to Arizona’s pioneering Groundwater Management Act of 1980. The act mandates that certain localities reach “safe yield” by 2025, balancing the amount of water pumped out of their aquifers with the amount that is replenished.

With less than four years to go, Tucson is the closest to reaching that goal. But according to a recent report from researchers at ASU, climate change, unrelenting drought and weaknesses in the 1980 act mean that Tucson—and Arizona—may still be far from a sustainable water future.

Over 80% of Arizona’s population lives within what are known as “Active Management Areas” or AMAs. In Arizona’s AMAs, the majority of the water supply comes from sources on the surface like the Colorado, Salt and Verde Rivers. Over a third comes from underground.

Prior to the Groundwater Management Act, the state’s groundwater supply was in trouble. By 1977, 2.5 million more acre-feet of groundwater was being pumped from the ground each year than was being replaced (an acre-foot is enough water to cover an acre one foot deep in water).

This process—called overdrafting—is untenable for a few reasons. It reduces the aquifer’s water supply and quality, increases the cost of pumping groundwater and can harm local ecosystems. And once too much water is pumped from the ground, the spaces between the rocks of the aquifer, once filled with water, collapse. Not only can this create fissures in the earth and cause the ground to sink, but it means the aquifer may not be able to fill back up with water in the future.

With these threats facing Arizona’s underground water supply, the state needed to act.

Under the 1980 law, the state identified five areas that rely heavily on groundwater and designated them as Active Management Areas. Among the act’s many restrictions and conservation requirements, it established the ambitious goal that three of the AMAs—Phoenix, Tucson and Prescott—would achieve safe yield by 2025.

With less than four years to go, Tucson is the nearest to striking that balance. According to data from the Arizona Department of Water Resources, the Tucson AMA was within 25,000 acre feet of safe yield for eight of the years between 2006 and 2016.

The Tucson AMA has succeeded in using less groundwater in part because it has relied increasingly on recycled water and water from the Colorado River. Unlike groundwater, which collects in the earth over the course of thousands of years, Colorado River water is considered a renewable resource by Tucson’s water authority because its flow is supplied each year by rain and melting snow.

But groundwater is still being overpumped in four of the state’s five AMAs. In some places, aquifer levels are declining. And climate change and drought are jeopardizing the state’s surface water alternatives.

According to researchers from ASU’s Kyl Center for Water Policy at Morrison Institute, state laws still allow unsustainable water pumping from aquifers, despite the existing legislation designed to make sure that water drawn from underground is replaced.

“While 'safe yield' was intended to be sort of a substitute for sustainable groundwater use, that's not the way it has played out,” Kathleen Ferris, co-author of the report and the Kyl Center’s senior research fellow, told The Arizona Republic. “We aren't really sustainably using our groundwater, and we have got to figure out a way to do that, or I don't see a really bright future in the long term.”

In their May report, Ferris and her co-author Sarah Porter wrote that despite the important gains the 1980 groundwater act has achieved, “significant weaknesses” still exist, and “conservation has not produced the cutbacks in groundwater use necessary to sustain this essential and limited resource.”

“We've made a lot of progress, but what this report points out is that we haven't gone far enough, because we are still overdrafting groundwater,” said former Arizona Gov. Bruce Babbitt in an interview with The Arizona Republic. Babbitt signed the 1980 act into law.

 “I believe it is the most important issue facing Arizona today and that the future of our state very much depends on legislative action, which is way overdue,” he told the paper.

Also contributing to the growing urgency to resolve Arizona’s groundwater management are dry conditions so severe scientists have called it a “megadrought.” Most of the West is currently experiencing extreme and exceptional levels of drought, as it has for much of the past two decades since the U.S. Drought Monitor began tracking the data.

As of early July, over 20 wildfires burned in Arizona, many kindled by dry vegetation. Drought has even threatened the state’s quintessential saguaro cactuses, which in recent years have begun sprouting unusual side blossoms and collapsing under their own weight, likely in response to the unusually dry conditions.

Extreme drought has also caused the Colorado River’s flow to drop—flows from 2000 to 2018 contained approximately 18% less water than the 20th century average. In early June, Lake Mead was at 36% capacity, the lowest level the lake’s been since nearly a century ago.

In 1993, the state completed the Central Arizona Project, a 336-mile long canal that carries Colorado River water southeast to central and southern Arizona and serves about 80% of the state’s population.

Tucson has increasingly relied on water delivered via the Central Arizona Project, most of which is sunk directly into the ground, where it mixes with groundwater and is later pumped out again for use. Though far from the river’s flow, in 2019 the Tucson AMA relied on the Colorado for over 50% of its water. But the Colorado River’s resources have become increasingly strained.

“While the use of Colorado River water delivered through the Central Arizona Project (CAP) has reduced reliance on groundwater, CAP water is now fully allocated and expected to decrease as climate change and long-term drought continue,” Ferris and Porter wrote in their report.

Tim Thomure, Tucson’s interim assistant city manager and former director of its water utility, told the Arizona Daily Star that “the city can withstand the deepest cut it’s likely to get from its supply of Colorado River water in the foreseeable future.”

While future cuts to the city’s Colorado River water supply may mean that Tucson has to pump more groundwater, Thomure told the paper that the aquifer has typically been replenished by enough rainfall and runoff to make up for the most likely worst-case scenarios.

Climate change, however, is still a threat. Groundwater availability and quality are subject to the variability and intensity of extreme weather events. A recent study from the U.S. Bureau of Reclamation found that climate change may actually reduce the amount of natural groundwater recharge that comes from rainfall and runoff.

Ferris and Porter warn that the state will need to increasingly rely on its uncertain groundwater supply as Central Arizona Project water becomes less available.

The ASU researchers wrote: “Central Arizona will be forced to rely more and more on groundwater, increasing the urgency to better manage it as a savings account for a dryer future.”

In the Tucson AMA, despite its success in nearing safe yield, some water management challenges remain.

According to the 1980 law, safe yield can be achieved across an entire groundwater basin. Under current regulations, water that’s pumped from one spot in the aquifer can be replaced elsewhere. In the Tucson AMA, this has resulted in an uneven recharging of the aquifer. So while the AMA as a whole is hovering near safe yield, the actual availability of water underground may depend on where you are over the aquifer.

Referred to as hydrologic disconnect, this phenomenon was identified as a major issue with the “potential to create or worsen localized groundwater depletion” in a March report by the committee responsible for strategizing water management in the state’s AMAs after 2025.

The committee also cautioned that large swaths of the populations living in AMAs are still groundwater-dependent, lacking access to renewable water supplies and the necessary infrastructure and creating “uncertainties as groundwater supplies become more limited.”

To address this, plans are in motion in Tucson on a series of pipelines that will bring Colorado River water from the Central Arizona Project to the city’s suburbs. This water is meant to ease the strain on groundwater in areas north and south of the city, which have been overpumping from the aquifer.

Some farmers in Arizona’s AMAs operate under a unique guideline. Those who used groundwater in the five years prior to January 1, 1980 were grandfathered in and allowed to continue to pump groundwater to irrigate their farm land.

According to the Groundwater Management Act, these farmers and certain other water users are under no obligation to replace the groundwater they pump. Today, agriculture is still the largest user of groundwater in the state’s AMAs and it is the largest contributor to unreplenished groundwater use in the Tucson AMA.

To offset the amount of water they pump, some farmers in the Tucson area participate in groundwater savings projects: Rather than irrigating their land with groundwater, farmers use Colorado River water instead. BKW Farms north of Tucson was the first facility of this type in Pima County. Since it began the arrangement in 1995, the farm has reduced its groundwater pumping by over 95%.

As of yet, it’s unclear what regulations will be in place for AMAs after 2025. As a result of the 1980 Groundwater Management Act, Arizona has drastically reduced its reliance on groundwater. More actions are needed, however, if the state’s AMAs want to reach and maintain safe yield and adapt to the changing climate.

Outside of the state’s AMAs, the situation is even more urgent: groundwater is unregulated and depleting fast. In Willcox, located a little over an hour east of Tucson, large farms are quickly draining local aquifers. Legislation introduced this year proposing groundwater rules for these areas faces opposition from some lawmakers and the agriculture industry.

In Tucson, officials are currently preparing a long-ranging master plan that looks ahead to the city’s water future in the year 2100. The plan, which will be completed within two years, looks at the area’s “population growth, climate change, economic development, conservation practices, and water quality” to prepare for possible futures. Part of the focus will be on how groundwater will be integrated into the city’s water management going forward.

“If Arizona is to prosper into the next century, our focus needs to turn to what is essential for our future: The preservation of our groundwater and our increasingly fragile aquifers,” Ferris and Porter wrote in their report. “Our own survival is at stake.”

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