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Arizona Considers Desalination Options for Future Water Supply

From a partnership with Mexico to treating brackish groundwater, Arizona is exploring opportunities to incorporate desalinated water into its long-term water supply planning.

Written by Jerry Redfern Published on Read time Approx. 5 minutes
Employees work at a desalination plant in Carlsbad, California.Don Bartletti/Los Angeles Times via Getty Images

Not if, but  when.

That’s the future of water desalination plants in Arizona, according to the head of the state’s water department. They are controversial and expensive, but Arizona’s current leadership views desalinated water – or “desal” – as key to the state’s long-term water plans. Arizona sits atop an estimated 600 million acre-feet of brackish water.

“Desalination is in our future,” said Thomas Buschatzke, director of the Arizona Department of Water Resources. In late 2016, the state formed a committee to study the feasibility of desalination for a region with rising population and droughts exacerbated by climate change. More recently, an international water treaty update with Mexico is another factor in the movement toward desalinated water in Arizona. “We are doing our due diligence to make that happen,” Buschatzke says.

But that future is still years down the road. While the basics of desalination are fairly straightforward, the practicalities are messy and expensive.

The process behind utility-scale desalination is called reverse osmosis. Saline water – either from an ocean or brackish underground aquifer – is forced through an extremely fine filter that strips the water of salts and other dissolved solids. The process takes a phenomenal amount of energy and the resulting wastewater – saturated with the unwanted salts and minerals – poses environmental concerns.

All of this makes desalination an expensive way to bring water to consumers.

Desalinated water can cost from several times more up to an order of magnitude more than surface water. But if rivers are running dry, adding a zero to a water bill may become an acceptable option. Currently Arizona is talking with Mexico about a possible plant on the Sea of Cortez, while a committee on the Governor’s Water Augmentation Council explores how to tap and treat the state’s 600 million acre-feet of brackish water – a potentially less expensive option. Either way, Buschatzke says that even ballpark estimates on either possibility are still years down the road.

But a couple of rough comparisons can be seen next door in California. Last year, Santa Barbara brought a desalination plant back online after it had been mothballed in the ’90s. The cost? About $71 million. And that doesn’t include $4.1 million a year in energy costs to squeeze seawater through the filters. The plant provides 30 percent of the water in a city of 91,000, although that amount could increase in the future.

Pipes for a water intake pump sit on an area of Pyramid Island that used to be under the waters of Lake Mead near Boulder Beach on May 13, 2015 in Lake Mead National Recreation Area, Nevada. Falling water levels in the lake and concern over long-term security has prompted Arizona to consider desalination. (Justin Sullivan/Getty Images)

Down the coast, the Claude “Bud” Lewis Carlsbad Desalination Plant cost $1 billion to build by the time it came online in 2015. It draws around 36 megawatts from a neighboring power plant to produce about 10 percent of the potable water used by the 3.1 million people of San Diego County.

Sandy Bahr, director of the Grand Canyon Chapter of the Sierra Club in Phoenix, notes that desalination plants aren’t a new idea for Arizona water planners. She says the idea comes up “pretty much every time” there is talk of the state water supply at the Capitol. And each time, the conclusion is the same: “What they find is that it’s very costly, takes a lot of electricity and there’s no good way to dispose of the brine.”

Bahr says she doesn’t necessarily have anything against the governor’s desalination committee. “Looking at things: I don’t think it does harm. But it does detract from things we can do right now,” she said. “They are looking for the magic solution – the magic bullet – and desal just isn’t that.”

The state should be much more aggressive in adopting strict municipal and agricultural conservation goals, and dramatically improve water reuse and recycling programs before desalination should be considered, she says. For example, Arizona agriculture accounts for 74 percent of state water use. The top three crops by acreage are hay, alfalfa and cotton – comparatively low-value crops considering their water requirements (as noted in this 2015 University of California, Davis study).

“We are in the Sonoran desert – we should act like it,” Bahr says.

“There’s no real big silver bullets out there in Arizona, so we’re going to have to cobble together several different ideas,” Buschatzke said. Those combine desalination with many of the same ideas Bahr mentions: improved conservation programs, water recycling and agricultural-to-municipal water rights swaps.

“Cost will drive a lot of what happens in terms of the timing,” he said, with the least-costly options happing first. “I think desal is further out in time – but it’s just a matter of time.” He thinks a minimum of 10 years, and quite possibly more.

He points out that, over decades, Arizona has implemented a series of widely hailed conservation efforts that have led to overall state water use equaling that of 1957 while the population has increased sixfold.

But one day, he says, the state will “squeeze the last drop” out of the water resources it has, and, “the market will help decide the when and the where for desal.”

The climate will factor as well. This winter’s snowpack has water managers across the Southwest worried for the coming summer. “The bad start to the water year is certainly weighing heavily on my mind,” Buschatzke said.

But one more wild card in Arizona’s desalination equation is Mexico.

The Colorado River Agreement apportions Colorado River water among seven U.S. states and Mexico. A recent update, called Minute 323, sets aside $31 million to study and improve Mexico’s water infrastructure and to consider building a desalination plant on the Sea of Cortez, about 50 miles from the Arizona border. That water could be piped to Arizona, or kept in Mexico and offset against that country’s allotment of Colorado River water.

This idea isn’t exactly new. “There’s been a kind of buzz that refuses to go away on this,” said Margaret Wilder, an associate professor at the University of Arizona School of Geography and Development and the Center for Latin American Studies.

Nine years ago, she headed a study group that traveled to Mexico and talked with government officials and other locals about just this possibility. She said her Mexican colleagues were receptive to the idea but concerned whether such a large infrastructure project would equally benefit those south of the border. They were also concerned about potential environmental damage from pumping high-salinity water back into the Sea of Cortez – environmental tourism is a major local industry.

“I think we need to advance as carefully as possible,” Wilder said.

But as hard as the development would be, Wilder says that a cross-border desalination plant may be likely. “Maybe not in my future,” she says, “but maybe my children’s future.”

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