The Colorado River is running dry. Is desalination the solution?
Arizona and Nevada agreed to a trade for desalinated water from the Pacific Ocean as the Colorado River dries.
As a megadrought and demands for irrigation and drinking water have reduced parts of the Colorado River to a trickle, water from a desalination plant in California is being proposed as part of a solution.
Northeastern University hydrology experts said that desalination, the process of removing salts and other minerals from water so it can be used by humans, will solve the river’s -and the western United States’ – water woes alone, however…at least not yet.
“Desalination works and has to work in some cases where we’re talking about societal collapse if you don’t get that water,” said Auroop Ganguly, distinguished professor of civil and environmental engineering at Northeastern. “We are probably not there yet for the Western U.S. to take that leap.”
The hottest and driest period in the last 1,500 years has reduced the Colorado River’s flow by 20% since 2000 compared with average flows in the previous century, according to the nonprofit Environmental and Energy Study Institute.
This megadrought combined with the lowest winter snowpack on record to reduce the 1,400-mile-long river, and the 250,000-square-mile river basin containing its tributaries, to approximately 36% of its storage capacity, the Bureau of Reclamation said in April. The bureau, which builds and manages water projects in the Western U.S., said these two factors have created “elevated risks to essential water and power infrastructure that supply water to more than 40 million people,” in the states of Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming.
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Earlier this month, however, a potential solution was proposed when the bureau and agencies in California, Nevada and Arizona signed a Memorandum of Understanding (MOU) for the San Diego County Water Authority to sell some of its water rights to the Colorado River to the inland states, because the utility has surplus water supplies from a desalination plant.
Desalinated water wouldn’t physically move inland under the proposed agreement, but the utility wouldn’t draw as much from the Colorado River as it’s entitled to because of its excess desalinated capacity. The amount of water to be sold, and its price, has yet to be agreed upon, according to the MOU.
“Next-generation strategies in the face of climate volatility must include interstate partnerships that deliver water where it’s needed most,” said Dan Denham, general manager of the San Diego County Water Authority. “New ideas are challenging to implement, but it’s in everyone’s best interest to make this work.”
Ganguly, who has visited Israel to study the country’s extensive desalination infrastructure, said there are three major problems with desalination as a panacea for the Western U.S.
First, he said it is expensive and energy intensive to desalinate water, which can be done by pumping seawater through semipermeable membranes to filter out the salt and other impurities, or by heating the seawater to distill it.
Transporting desalinated water also requires an extensive network of pipes, pumps, and other infrastructure, Ganguly said, which would take years and vast amounts of money to build across the western U.S.
Brine, or highly concentrated salt that is produced by desalination, must also be treated as wastewater. To do this at the necessary scale would also require years and huge amounts of money.
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For some countries in the Middle East and Northern Africa, these costs and obstacles are surmountable because fresh water is so rare. Qatar relies on desalination for 99% of its drinking water, for example; Kuwait depends on the technology for 90% of its drinking water, according to Al Jazeera; while the Mediterranean Sea will provide up to 80% of Israel’s potable water with the addition of their latest desalination plant, the Times of Israel reported in January.
“A lack of freshwater is “an existential crisis” for Saudi Arabia, Ganguly added. But he noted the oil-rich country has the energy resources to desalinate and has “invested significantly” over years in transporting water inland and solutions for brine.
And while the water situation in the Western U.S. “is dire,” according to Ganguly, droughts are “a slow-moving problem,” because they gradually make things worse as opposed to natural or man-made events such as hurricanes or wars.
Somnath Mondal, a postdoctoral researcher at the Roux Institute on Northeastern’s Portland, Maine, campus, explained that the western United States is susceptible to several weather patterns, including the Pacific Decadal Oscillation and El Niño. Those patterns have interacted and – with climate change – reduced rainfall over the western states. If the patterns change from their current position, however, the rains could return and mitigate the drought, Mondal, who previously worked as a hydrological modeler with the Arizona Department of Water Resources, said.
Meanwhile, simply bringing desalinated water to an already arid earth will likely affect evaporation patterns and the intense summertime monsoons that the region has historically seen in ways that are not yet understood.
“In the case of the Western US… they have an understanding that ‘a wet spring follows a dry summer and a dry spring follows a wet summer,’ in terms of summer rainfall,” Mondal said. “They have not checked whether [making] a spring wet by bringing more water for irrigation, whether that can have an influence on monsoon strength as well as the onset of monsoons.”
Instead of relying solely on desalination for a solution to the West’s water woes, Mondal said that the western states should focus on water storage and conservation to have “a fighting chance,” against the drought.
Ganguly agreed. “Desalination as a technology is there…it’s good to have in our portfolio,” Ganguly said. “But it is still a little bit of a last resort.”
