Why Desalination Won’t Save States Dependent on Colorado River Water

The Colorado River circles Horseshoe Bend in the Glen Canyon National Recreation Area in Page, Arizona.

Rhona Wise | Afp | Getty Images

States dependent on the drought-hit Colorado River are increasingly turning to desalination as a way to fill the river’s scarcity and boost water supply in the western United States.

The search for alternative ways to get water comes as federal officials continue to impose mandatory water cuts for states that take water from the Colorado River, which supplies water and electricity to more than 40 million people.

Desalination (or desalination) is a complex process that involves filtering out salts and bacteria from ocean water to produce safe drinking water for tap water. Although there are more than a dozen desalination plants in the US, mostly in California, the existing plants cannot replace the amount of water the Colorado River is losing.

“Ocean water desalination has a huge appeal,” said Robert Glennon, professor emeritus of law and water policy researcher at the University of Arizona. “The thought is that if we can just get the salt out of the water, everything can be fixed. But it’s a kind of siren song that will turn out badly.”

According to water policy experts, desalination plants are costly to operate, require huge amounts of energy and are difficult to manage in an environmentally sound manner.

The debate about whether desalination can solve the Colorado River’s drying up problem comes as a historic mega-drought swept the western US, causing the region’s driest two decades in at least 1,200 years. Water levels in the country’s two largest reservoirs, Lakes Mead and Powell, have reached their lowest levels on record.

Drinking water pipes are shown at the Poseidon Water desalination plant in Carlsbad, California, USA on June 22, 2021. The picture was taken on June 22, 2021.

Mike Blake | Reuters

The Biden administration called on seven states in the Colorado River basin to save 2 to 4 million acre feet of water, or up to a third of the river’s average flow. But water managers say much more drastic savings will be needed as dry conditions worsen in the basin.

Katherine Sorensen, who leads research at the Kyle Water Policy Center at Arizona State University, said that while there has been significant progress in the West on water conservation, the Colorado River is heavily congested and low reservoir levels are “extremely problematic.”

“We are taking more water from the river than Mother Nature can provide,” Sorensen said. “The river is a super important resource for all of us.”

The cost of water is high

Because desalination is a drought-tolerant process, some argue that states with such facilities could become less dependent on water from the Colorado River. But the cost of desalination is high compared to the cost of imported river water, and the process requires a lot of energy to separate salts and other dissolved solids from the water.

Large power plants require “tens of megawatts” to operate. according to Department of Energy, and energy consumption is the largest component of desalination operating costs, accounting for about 36% of total operating costs.

For example, the Carlsbad desalination plant in San Diego, California requires about 35 megawatts of electricity to operate. (For comparison, 1 megawatt is enough to power a small city, and 1,000 megawatts is enough to power a medium-sized city.) The plant produces an average of 50 million gallons per day, which is only about 10% of the total drinking water required by San Diego.

The cost of desalinated water in Karlovy Vary is estimated at $2,725 per acre-foot. recent analysis environmental economist Michael Hahnemann of Arizona State University. This is significantly more than the amount the San Diego County Water Authority pays for water received from the Colorado River and the Sacramento-San Joaquin Delta. Last year, the Water Department offered to increase his rate to $1,579 per acre foot for raw water in 2023.

“The technology for desalination has improved a lot, and now it is practically possible to do it,” said Jay Lund, co-director of the Watershed Science Center at the University of California, Davis. “But that’s only possible if you’re willing to pay a lot of money.”

Water policy experts have also long discussed the possibility of using water from the Sea of ​​Cortez in Mexico, the closest sea to Arizona. In fact, Arizona officials voted in December to move ahead with studying a $5 billion project led by an Israeli company to build a seawater desalination plant in Mexico and transport it through a pipeline that would pass through Organ Cactus National Monument.

The company leading the project said it will supply up to 1 million acre feet of water to Arizona, roughly the same as the amount the central and southern parts of the state used from the Colorado River in 2022. The first phase of the plan will be a single pipeline that will transport about 300,000 acre feet of water to Arizona, with future pipes delivering up to 1 million acre feet.

If desalinated water should have cost $2,000 to $3,000 per acre foot for a plant in Mexico, then the cost could potentially be nearly $1 billion per year for 300,000 acre feet of water. And the cost can reach nearly $3 billion a year for 1 million acre feet of water.

Environmental costs of desalination

Desalination is also associated with environmental costs. In addition to greenhouse gas emissions resulting from the large amount of energy required to operate, the process leaves residual brine or concentrated salt water that can increase the salinity of seawater and, as a result, damage local marine systems and water quality.

The brine may contain toxic metals such as mercury, cobalt, copper, iron, zinc and nickel, as well as pesticides and acids, cause irreversible changes in the environment.

“It is difficult to scale up desalination projects because desalination is extremely expensive and there are real problems with disposing of the remaining brine,” Sorensen said.

One study published in ScienceDirect found that brine volumes exceed most industry estimates, averaging one and a half gallons for every gallon of fresh water produced. The authors strongly recommended brine management strategies that limit negative environmental impacts and reduce the economic costs of disposal.

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However, the most common current practice is to dump the remaining brine back into the ocean. which led to loss of fish and coral populations, and damage to algae and fish larvae.

California regulators last year denied construction of a $1.4 billion desalination plant in Huntington Beach, citing not only the cost of water, but also the danger to marine life and the risks associated with rising sea levels and flooding.

Desalination will be useful in some areas of the country, especially as operating costs come down and more research is done on brine disposal. But water policy experts have come up with alternatives that are currently less expensive and energy intensive and do not pose a risk to the environment.

Lund said low-value fallow farming is a cheaper and better alternative from a national and state perspective, as farming uses roughly 80% of the Colorado River’s water. “This is the cheapest and most sustainable way to bring the system back into balance,” Lund said.

Reusing wastewater, conserving water and encouraging redistribution of water are other sustainable solutions to water scarcity that should take precedence over desalination, Glennon said.

“Desalination is not a silver bullet. There are huge challenges ahead of us,” Glennon said. “We can do it, there’s no doubt about it, but it’s not the only option.”

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