The Colorado River meanders around Horseshoe Bend in Glen Canyon National Recreation Area in Page, Arizona.
Rauna War | AFP | Getty Images
States dependent on the drought-stricken Colorado River are increasingly looking to desalination to correct river losses and boost water supplies in the western US.
The search for alternative ways to source water comes as federal officials continue to enforce mandatory water cuts For those states that are served by the Colorado River, which supplies water and electricity for more than 40 million people.
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Desalination (or desalination) is a complex process that involves filtering out salt and bacterial material from sea water to produce safe drinking water for the tap. While there are more than a dozen desalination plants in the US, mostly in California, the existing plants do not have the capacity to reduce the amount of Colorado River water.
“There is tremendous allure in desalination of sea water,” said Robert Glennon, professor emeritus of law and water policy scholar at the University of Arizona. “The idea is that if we take the salt out of the water, everything can be fine. But it’s a mermaid song of sorts that will go bad.”
According to water policy experts, desalination plants are expensive to operate, require enormous amounts of energy and are difficult to manage in an environmentally friendly manner.
The debate over whether desalination could be a solution for the drying up Colorado River comes as a historic megadraft produced the driest two decades in the region. at least 1,200 years, Water levels in Lake Mead and Lake Powell, the nation’s two largest reservoirs, have reached their lowest levels on record.
Pipes containing drinking water are shown at the Poseidon Water Desalination Plant in Carlsbad, California, US, on June 22, 2021. The picture is taken on June 22, 2021.
Mike Blake | reuters
The Biden administration has urged seven states in the Colorado River basin to save 2 million to 4 million acre feet of water, or up to one-third of the river’s average flow. But water managers say the savings will need to be more drastic as drought conditions worsen in the basin.
Katherine Sorensen, who directs research at the Kyle Center for Water Policy at Arizona State University, said that while some major progress has been made on water conservation in the West, the Colorado River is severely aggregated and low reservoir levels are “extremely problematic.”
“We’re taking more water out of the river than nature can really provide,” Sorensen said. “The river is a vital resource for all of us.”
water costs more
Since desalination is a drought-resistant process, some have argued that states with such facilities could find themselves less dependent on Colorado River water. 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 salt and other dissolved solids from the water.
Large scale plants require “tens of megawatts” to operate, According to Energy Department, and energy consumption is the largest component of desalination’s operating expenses, comprising approximately 36% of total operating expenses.
For example, the Carlsbad Desalination Plant in San Diego, California requires about 35 megawatts of electricity to operate. (By comparison, 1 MW is enough energy to operate a small town and 1,000 MW is enough to power a medium-sized city). The plant produces an average daily flow of 50 million gallons, which is about 10% of the total drinking water needed by San Diego.
The cost of desalinated water in Carlsbad is estimated at $2,725 per acre-foot. recent analysis by Michael Hannemann, an environmental economist at Arizona State University. This is significantly more than the amount the San Diego County Water Authority pays for water it receives from the Colorado River and the Sacramento San Joaquin River Delta. water authority last year proposed to raise the rate $1,579 per acre-foot for untreated water in 2023.
“Desalination technology has improved a lot and it is now remotely possible to do this,” said Jay Lund, co-director of the Watershed Sciences Center at the University of California, Davis. “But it’s only plausible if you’re willing to pay a lot of money.”
Water policy experts have also long debated the possibility of taking water from Arizona’s closest sea, the Sea of Cortez in Mexico. In fact, Arizona officials voted in December to advance studies of a $5 billion project led by an Israeli company that would build a plant to desalinate seawater in Mexico and connect it to a pipeline. which will cross through Organ Pipe Cactus National Monument.
The company leading that project said it would give Arizona up to 1 million acre feet of water, roughly the amount the central and southern part of the state used from the Colorado River in 2022. The first phase of the plan would be a single pipeline that would transport about 300,000 acre-feet of water to Arizona, with future pipes supplying up to 1 million acre-feet.
If desalinated water had to spend Between $2,000 and $3,000 per acre-foot for the Mexico plant, so the cost could potentially be up to about $1 billion per year for 300,000 acre-feet of water. And the cost for 1 million acre-feet of water could reach nearly $3 billion per year.
environmental cost of desalination
There are also environmental costs to desalination. In addition to the greenhouse gas emissions produced by the large amount of energy required to operate, the process leaves behind residual brine, or concentrated salt water, which can increase the salinity of seawater and result in damage to local marine systems and water. may harm the quality.
Brine can contain toxic metals such as mercury, cobalt, copper, iron, zinc and nickel, as well as pesticides and acids. Causes irreversible changes in the environment.
“Desalination projects are difficult to scale up because desalination is extremely expensive and there are real problems with disposing of the leftover brine,” Sorensen said.
a study published in the journal ScienceDirect found that the amount of brine exceeds most industry estimates, including an average of a gallon and a half for every gallon of fresh water produced. The authors urge brine management strategies that limit negative environmental impacts and reduce the economic cost of disposal.
However, the most widespread current practice is to dump the remaining brine back into the ocean, caused by Damage to fish populations and coral as well as damage to sea grass and fish larvae.
California regulators last year rejected a $1.4 billion desalination plant in Huntington Beach, citing not only the cost of the water but the dangers to marine life and the risks associated with sea level rise and flooding.
Desalination will be useful in some areas of the country, especially due to lower operating costs and more research being done on brine disposal. But water policy experts have suggested alternatives that are currently less expensive and energy-intensive and do not pose a threat to the environment.
Lund said low-cost farming is a cheaper and better option from a national and state perspective, since agriculture uses about 80% of the Colorado River’s water. “It’s the cheapest and most sustainable way to bring the system back into balance,” Lund said.
Glennon said that encouraging wastewater reuse, water conservation and water reallocation are other sustainable solutions to water scarcity that should be prioritized over desalination.
“Desalination is not a silver bullet. The challenges are immense,” Glennon said. “We can do it, there’s no doubt about it – but it’s not the only option.”
