During his last year in office, Gov. Doug Ducey is trying to create a legacy of water security in drought-stricken Arizona. But his most ambitious effort in that quest could end up being in Mexico.

In his last state of the state speech in January, he proposed an investment of $1.16 billion over the next three years to make the state “more resilient to drought, secure a sustainable water future and allow for continued growth.”

The goal, he said, is to “secure Arizona’s water future for the next 100 years.”

The governor’s office shared a plan with lawmakers late last month to create a new statewide water authority tasked with boosting water supplies by developing and supporting innovative water augmentation efforts.

Among the potential projects that the agency could develop are desalination plants in Mexico, which would create freshwater by removing salt from seawater. Arizona and other Lower Basin states would take some of Mexico’s shares of Colorado River water in exchange for the water they financed desalinating south of the border, according to Arizona Department of Water Resources Director Tom Buschatzke.

“We’re trying to stay ahead of the curve and make sure that we have resilient water supplies, for the growing economy, for the people, for the environment and for the lifestyle that Arizona people are used to seeing,” said Butschatske.

Historic Threshold Adds Urgency to Water Woes

Staying in front of that curve is increasingly difficult in the Southwest.

Last week, for the first time since it was filled 50 years ago, the water level in Lake Powell, the second-largest reservoir in the country, dropped so low that it threatens the ability of Glen Canyon Dam to generate electricity for some 6 million customers that depend on it. The U.S. Bureau of Reclamation announced on Wednesday that the reservoir in the Upper Colorado River Basin had fallen below the 3,525-foot target elevation that provides a 35-foot buffer before declining water levels reach the minimum required to spin the dam’s turbines. The water level is expected to recover by May, but its supply of water will remain perilously diminished.

And Lake Powell is not the only critical, southwestern reservoir running low.

In August, the Bureau of Reclamation declared a water shortage for the first time in Lake Mead, the largest reservoir in the country, which is formed by the Hoover Dam in the Lower Colorado River Basin.

Colorado River water, originating from the snowpack of the southern Rocky Mountains, flows 1,450 miles southwest to Mexico and the Gulf of California. It travels through seven states and two nations, providing water to more than 40 million people and about 5 million acres of farmland.

But thinner snowpacks, declining precipitation and increasing temperatures from climate change have led to a prolonged drought in the West that has lasted more than two decades, posing a risk for water security throughout the Southwest. 

“This year the Colorado River Basin has experienced extremely variable conditions with a record high snowpack one month, followed by weeks without snow,” said Reclamation Acting Commissioner David Palumbo in the announcement. “This variable hydrology and a warmer, drier West have drastically impacted our operations and we are faced with the urgent need to manage in the moment. 

The river’s flow has declined at least 20 percent since 2000 and is expected to decline more than 9 percent for every degree Celsius of warming, according to the U.S. Geological Survey. 

The drying coincides with a rapid increase in population in the region, especially in Arizona, which was third in population growth and migration gains from 2020 to 2021, following Texas and Florida.

Pricey Solution Supplies a Fraction of the Need

The most ambitious proposal to slake the region’s growing thirst as its most critical reservoirs decline is to build two desalination plants in Puerto Penasco, a Mexican city more than 60 miles south of the U.S.-Mexico border. Seawater would be pumped from the Gulf of California, also known as the Sea of Cortez, between the peninsula of Baja California and the Mexican mainland to the plants in the state of Sonora.

After its salt is removed, the water would be delivered to the Morelos Dam in the U.S.-Mexico border, where Colorado River water is distributed south of the border. With the freshwater satisfying U.S. commitments from the Colorado River to Mexico, more of the river’s flow could be held back for use in Arizona.

Some experts say that the high cost of desalination, the amount of energy it requires and the difficulty of disposing of brine, a salt-concentrated byproduct of seawater desalination, can be cause for concern. And the projects will only make up for a fraction of the Southwest’s water shortfall.

According to a 2020 binational study involving Lower Colorado River Basin states and Mexico, the plants would produce upwards of 200,000 acre-feet of desalinated water each year for a price of about $2,000 per acre-foot, making up for less than a fifth of the water deficit the Lower Basin states and Mexico are expected to see by 2030.

The capital to establish the plants would cost more than $3 billion, the study reported, and annual operating costs could range from more than $70 million to as high as $119 million.

“In almost all cases, desalination would be the most expensive way to produce water, and the reason it would be the most expensive way to produce water is because it requires a lot of energy,” Treavor Boyer, an associate professor of environmental engineering at Arizona State University who researches water sustainability.

The process of desalination leaves behind concentrated waste in brine that is many times saltier than seawater. Properly disposing of it often requires dispersing it gradually, farther out to sea than where the water to desalinate is being pulled, a process that was recommended by the binational study.

Mexico’s National Commission of Water and Secretariat of Environment and Natural Resources proposed that any concentrated salinity discharge into the waters of Mexico not exceed the ambient salinity concentration by more than 15 percent at a distance of 328 feet from the discharge point.

“You usually can’t just sort of put it right back in the immediate vicinity of where you would through the seawater because that salinity would be much higher than what the aquatic plants and animals are used to and it would be very detrimental to them,” said Boyer.

The primary technology the study recommended for desalination was reverse osmosis, which, according to Boyer, leaves some salt in the water, requiring less energy than if the plants were producing potable water. 

The details of how the plants would be powered and how the brine would be managed remain to be determined with Mexico, Butchatske said.

A Drought-Proof Supply

Despite the cost and potential for environmental harm, water policy experts are not opposed to the idea, although they are watching energy and waste issues. Many note the importance of diversifying state water sources. There is only so much water to distribute to the booming population, and every method of increasing the supply has environmental downsides, they point out.

“It’s a more drought-proof water source than some others, and so we think it has a place in our overall picture of the water supply along with others that are less expensive,” said Sharon Megdal, director of the University of Arizona Water Resources Research Center.

While not opposed to the idea, some say that groundwater regulation needs to be prioritized more than desalination.

“While it’s great that they are interested in investing lots of dollars, we think that it needs to be paired with the right policy,” said Haley Paul, Policy Director for Audubon Southwest.

She is among the water policy experts and lawmakers who are pushing for groundwater regulation in the state. Arizona, the only state in the Colorado River Basin that does not regulate all of its groundwater, has no limitations on how much water can be pumped from aquifers in rural parts of the state, leading to overdrafts that are drastically driving water levels down.

From 1957 until now, Arizona’s water use has declined slightly, Buschatzke said, “even though our population has gone up almost seven times and our economic output has gone up about 20 times.”

He chalked up the decline to conservation efforts that have driven down usage. Much of what used to be farmland in central and southern Arizona is now full of homes, which require substantially less water, he added. However, growing demand and the drought-dried supplies are challenging existing conservation efforts, leading to calls for long-term solutions like desalination from proponents of the project.

“We want to make sure that investors in the community know that their investment is going to be protected if they come to our state,” said Butschatzke. “We want people who buy houses to know that they’re protected, that they’re going to have water for their houses today into the future.”

Getting the desalination plant running could take about a decade. The two countries have not made an official deal and are planning on doing more studies to determine the details of the projects, Buschatzke said.

The new water authority could also potentially support rural groundwater management as well as technologies to conserve and reuse water.

Policymakers understand that addressing water security in the region is complex and calls for a “suite of options,” said Megdal.

“There aren’t necessarily quick fixes,” she said. “There aren’t necessarily cheap fixes.”