New Arizona water report brings some optimism

Research effort spanned 3 1 / 2 years, funded by AZ Board of Regents

Joan Meiners

Arizona Republic USA TODAY NETWORK

With Arizona’s access to Colorado River water as precarious as a fictional crack in the Glen Canyon Dam that retains less of it each year, tensions over water supplies in the state are rising while actual storage levels drop.

That many Westerners saw this coming for decades — watching the forces of climate change, population growth and development outstrip the capacity of a shrinking river to provide for the 40 million people who now rely on it — has not helped avert stalemated negotiations over modified use among seven Colorado River Basin states.

But it inspired a large, collaborative research effort to better understand the reliability of in-state water supplies. That work, requested by the Arizona Department of Water Resources and funded by the Arizona Board of Regents, spanned 3 1 / 2 years and drew upon the expertise and legwork of more than 40 faculty members, students and postdoctoral scholars across Arizona’s three major universities. The team made their conclusions public this week.

The Arizona Tri-University Recharge and Water Reliability Project released the findings on June 17 — and included some hopeful revelations. The Arizona Republic reviewed an embargoed copy of the report.

Among the research products aimed at facilitating improved watershed management are hydrologic profiles for each of the state’s 51 groundwater basins, as well as a statewide profile illuminating the overall balance of inflows and losses.

The elaborate individual basin summaries compare historic precipitation, evapotranspiration, recharge, runoff and air temperatures with modern flows and records across these landscapes to calculate changes in how much water evaporates or is absorbed by plants before the remainder runs off into underground aquifers and becomes available for

later use through groundwater pumping.

“These models are incredible,” said Neha Gupta, a professor at the University of Arizona who managed that school’s branch of the project after her graduate adviser and former project lead, Thomas Meixner, was killed on campus in 2022. “We’re actually able to model loss of terrestrial water storage in the Earth. It shows that we are losing water out of our system and that there’s also a warming signal.”

Projected changes in temperature, precipitation, recharge and runoff by the end of this century, defined as 2060 to 2099, forecast a drier future for already- parched Arizona compared with the historical period of 1981 to 2020.

The researchers linked an overall reduction in water storage to the influences of climate change, concluding that the reduced supply is “highly correlated with hotter and drier weather”patterns, which extensive prior work has tied to the warming effects of greenhouse gases emitted by humans burning fossil fuels like oil, gasoline and natural gas. This affects communities that rely on water transports from the Colorado River as well as those using local sources.

“Climate change impacts are reducing the flow in the river over time, in large part due to increasing temperatures affecting snowpack and surface runoff,” the report states. “The combination of over-allocation and reduction in average flows have resulted in the major Colorado River reservoirs, lakes Powell and Mead, being at the lowest levels since the reservoirs were initially filled.

This means that Arizona is no longer able to take its full allocation of CAP water, and deliveries within the state have been significantly curtailed. There is no obvious relief in sight.”

Finding ways to capture and store water

Despite this grim overall outlook for Arizona’s water future, the report struck a positive note by compiling a matrix of recharge opportunities, or ways management shifts might capture larger volumes of water for storage.

These include coordinating with municipal districts to redesign floodways and stormwater controls to maximize flow capture underground, incorporating more dry wells, infiltration trenches and permeable pavement into urban spaces, depositing plowed snow more strategically, and collaborating better with agencies like the Arizona Department of Transportation and the U.S. Forest Service to manage runoff while protecting natural wetlands, streams and springs.

With more than 95% of the precipitation that falls in the state “lost through evaporation and/or transpiration by plants,” according to a report summary, opportunities to boost supplies by finding ways to reduce these losses, “even by small percentages,” are promising even as a warming climate and growing water demands add challenges.

“We are a pro-plant, pro-environment team,” Gupta clarified when asked about the phrasing of plant use as water lost. “When we say the word ‘lost,’ that’s really where water goes back into the atmosphere and into this much larger system where we’re not able to recover it so it can be used in other ways. Reducing loss in the right ways can benefit forest health, wildfire risk and better support trees. And it looks like there’s some pretty strong potential to get water back into the ground.”

That potential to capture and store large volumes of water that would otherwise be lost to the atmosphere is greatest in the Mogollon Rim area, the researchers found, due to higher regional rainfall there compared to evaporation rates. In this cooler, biodiverse region between Flagstaff and Payson, as well as elsewhere in the state, the report suggests that adjusting land management efforts and infrastructure design to focus more on aquifer recharge efforts — through channeling flood flows, thinning forests and honing wildfire efforts — could greatly increase water reliability statewide.

“The Mogollon Rim is one of the highest elevation parts of the state, and it represents the upper part of two of the most productive watersheds in the state, the Salt and the Verde,” Gupta said.

“A lot of our population centers are lower in the watershed, so the idea is if you manage your watersheds on the whole, getting more water into the ground higher up is likely to benefit people downstream.”

Arizona’s current legal system lacks much regulation or monitoring of groundwater pumping outside of designated active management areas, which are typically limited to watersheds surrounding urban centers. The state also generally recognizes aquifer sources as separate from surface flows. Various national policies and court cases have also artificially distinguished the two.

That’s a public misunderstanding and a management issue, the researchers from the University of Arizona, Arizona State University and Northern Arizona University point out, because 32% of surface water in the state springs from underground, while in other areas groundwater basins are recharged by surface flows.

Their report out this week pushes back on this scientific fallacy by showcasing the many ways aboveground streams could be better integrated with aquifer storage to help offset water shortages with more mindful management. (Surface and groundwater systems can sometimes be effectively disconnected in especially deep groundwater basins, Gupta said, but in most of Arizona’s diverse landscapes the reality is more interconnected.)

Abe Springer, a professor at NAU, has been monitoring intricate exchange pathways between surface and groundwater sources and tracking water quality at natural springs across the Grand Canyon region for decades. His work recently gained new importance after the Dragon Bravo wildfire at the North Rim altered these landscapes and water sources in ways his team is now well positioned to evaluate. “Among the recharge options, karst aquifers with sinkholes, including limestone and related rock types, and areas of faults and fissures provide major opportunities to infiltrate and recover water quickly,” said Springer, who led the tri-university research effort at NAU, about the new report. “Getting water underground before it has a chance to evaporate is an important path towards enhancing recharge.”

Optimism also found in state-focused research surviving cuts and tragedy

At a time of widespread setbacks to science and research funding in the United States, members of the Arizona Tri-University Recharge and Water Reliability Project expressed optimism not only about in-state water management opportunities, but also simply about their ability to complete such a largescale climate-related research effort.

“(This project) has been a great demonstration of how academics can work together with stakeholders and external partners to develop information to support water resources across the state of Arizona while also taking a leap forward on behalf of science,” said Gupta, emphasizing the value of state-funded research to address local concerns.

Recent slashes to research funding and university support across the country under President Donald Trump have derailed similar projects that depend on federal funding or agency input, with future environmental and economic consequences yet unknown as longterm monitoring data goes uncollected.

With climate change intensifying storms, drought, wildfires and more, scientists say this type of information is needed more than ever for public safety and to avoid costly damage to the natural systems, such as watersheds, upon which humans heavily rely.

“Given the current concerns about the reliability of Colorado River deliveries to Arizona, this is a critical time to be thoroughly exploring our water supply options,” said Kathy Jacobs, the lead professor on the project based at the UA, in a press release about the report. “This project has built a solid scientific foundation for maximizing water supplies that are currently lost to the atmosphere, in order to support communities and natural habitats across the state.”

The research has been granted a oneyear no-cost extension by the Arizona Board of Regents, meaning the work will continue through June 2027 without additional funding.

The scientists and students involved remain inspired by the memory of their original leader on this ambitious undertaking. In a press release, the collaborative unit made a point to “acknowledge the contributions of Dr. Thomas Meixner, the original principal investigator of this project. We are all motivated by his memory and proud to complete this project in his honor.”

Gupta told The Republic that this has been a strong focus of hers in particular. She came to Arizona to study with Meixner, and spent six years as his student before his death. She will now take over from Jacobs to lead the initiative through its last unfunded year — for the future of science and Arizona’s water supply, and in memory of her mentor.

“After we really tragically lost him, the team really decided that we also wanted to make sure to carry out this project as a great way to honor his legacy and everything that he did, and the type of researcher he was.”

Joan Meiners is the climate news and storytelling reporter at The Arizona Republic and azcentral.com. Her journalism for various outlets has won national awards for investigative reveals, feature writing, business reporting and innovative climate coverage. Before becoming a journalist, she completed a doctorate in ecology with a focus on native bees. Send tips or questions to joan.meiners@arizonarepublic.com or follow her work on Instagram at @joan_bikes_arizona.