The Bureau of Reclamation this week flipped the switch on the dormant Yuma Desalting Plant in Arizona, launching a yearlong test to determine whether the 18-year-old facility can finally live up to its promise to help solve the Colorado River Basin's water supply challenges.

The pilot run, which began Monday, will also be a test of a landmark agreement involving the United States, Mexico and a coalition of environmental groups to protect a vast Mexican wetland that depends on the salty agricultural runoff that will now be diverted to the plant, where it will be cleaned and released into the Colorado River.

The $250 million plant was built in 1992 to help meet treaty obligations requiring the United States to send 1.5 million acre-feet of clean Colorado River water to Mexico each year. But nine months after signing the treaty, plant managers shut down the facility after a flood damaged an intake canal. Ample flows in the Colorado River Basin in the ensuing years rendered the plant unnecessary.

Now, with a prolonged drought parching the Lower Colorado Basin -- and with Arizona, Nevada and California scrambling to avoid water shortages amid rising demand -- the plant has taken on renewed importance (Land Letter, March 22, 2007). Water providers are hoping that the pilot project, which will treat 29,000 acre-feet of runoff from Arizona farms and discharge the cleaned water into the Colorado River just above the U.S.-Mexico border, will demonstrate that the plant can be operated on a long-term basis.

With the plant helping to meet the United States' treaty obligations to Mexico, Reclamation can leave more water upstream in Lake Mead for use by domestic users, including California's Metropolitan Water District, the Southern Nevada Water Authority and the Central Arizona Water Conservation District.

The three entities, which are helping to pay for the $23 million pilot project, will receive water credits in Lake Mead to help slake the thirst of Las Vegas, Phoenix, Los Angeles and other cities during the pilot run.

The Bureau of Reclamation this week launched a 365-day pilot run of its Yuma Desalting Plant near Yuma, Ariz. If successful, the plant could be restored to full capacity, providing water for municipalities in California, Arizona and Nevada. Photo courtesy of BuRec.

"Drought, population growth and the impacts of climate change on water in the Southwest have increased the stress on the Colorado River," said Anne Castle, assistant Interior secretary for water and science, in a statement. "These collaborative undertakings ... exemplify the types of partnerships needed to stretch available supplies to meet both current and future water needs."

Angel Santiago, vice chairman of the Metropolitan Water District's board of directors, said the project "will be critical in conserving supplies for future use," particularly given current drought conditions in California.

The amount of water each entity receives will correlate with its financial contribution to the project. The Metropolitan Water District will pay 80 percent of the cost in return for 80 percent of the water. Arizona and southern Nevada will each get a 10 percent share. In all, the three entities will pay for about $14 million of the pilot run's cost. The federal government will pay the $9 million balance.

The plant will run at one-third capacity for 365 days, which could be spread across 18 months depending upon how often the plant needs to be taken offline for maintenance or evaluation, said Jennifer McCloskey, area manager for Reclamation's Yuma, Ariz., office.

BLM conducted a 90-day demonstration run at 10 percent capacity in the spring of 2007 but concluded that a longer test was necessary to determine whether the plant could be operated on a long-term basis. That test run showed encouraging results, McCloskey said, adding that she is optimistic that the plant will prove its mettle in the new, bigger pilot run.

"My confidence level for the operation as a pilot run is very high," she said. "All the work was done up-front, in the planning stage, and now it's just smooth sailing."

Protecting the wetland

Ecologically, however, it remains to be seen whether Reclamation can operate the plant at one-third capacity while still protecting the Cienega de Santa Clara, a vast wetland south of the border.

The closure of the plant, located about 5 miles west of Yuma, Ariz., resulted in an incidental ecological benefit for the wetland. Highly saline agricultural runoff that would have been diverted for treatment was rerouted into the Colorado River Delta, bypassing the Lower Colorado River and expanding the Cienega de Santa Clara to 40,000 acres.

Concerned that the reopening of the plant would destroy the Cienega, which has become an important stopover for migratory birds and provides habitat for 95 species, environmental groups fought the proposal for years. But under the new agreement, parties on both sides of the border will provide 29,000 acre-feet of replacement water to make up for the loss of high-salinity flows to the wetland.

A pair of environmental groups -- Environmental Defense Fund in the United States and ProNatura Noroeste in Mexico -- have purchased water rights from Mexican farmers, freeing up irrigation water. The United States has committed to diverting excess water from the Colorado River during rainstorms to the wetland. Mexico has not yet revealed how it plans to meet its obligations under the agreement.

Jennifer Pitt, a senior resource analyst for Environmental Defense who has worked for years to protect the wetland, said she believes the agreement will ensure that the wetland stays wet while the desalting plant is in operation over the next year or so.

"To me, not only have we achieved important protection, but it's also the first time the U.S. or Mexican governments have, separately or together, sent water resources to an environmental resource in the delta," she said. "That is a really good turn of events, and demonstrates that it can be done -- there's a spirit of cooperation that hasn't been there in the past."

"Two years ago, we didn't dream of this," added McCloskey, the Reclamation manager. "We didn't know this could be done."

That cooperation could also help provide a foundation for future agreements if the plant is fully restored, Pitt and McCloskey said.

But another Lower Colorado River project designed to stretch water supplies in the basin could complicate future efforts to secure water for the delta.

Along with the Yuma Desalting Plant pilot run, Reclamation is also constructing the $172 million Drop 2 storage reservoir project, located in Southern California about 30 miles west of Yuma. That project will store excess water flowing down the Lower Colorado River during rain events for use by the Imperial Irrigation District.

While that project, like the desalting plant, will allow Reclamation to leave more water in Lake Mead for cities, it will capture the same water that Reclamation is now using to help replenish the Cienega de Santa Clara during the pilot run of the plant.

McCloskey said the Drop 2 reservoir system is complex and it is unclear whether it could be operated to allow for releases to the wetland. "We'd have to think a lot more about it," she said. "We have a lot to learn about how we're going to be able to use Drop 2."

Thanks to recent heavy rains, Reclamation has already met its requirement to send about 10,000 acre-feet to the Cienega to offset the loss from the desalting plant's pilot run, she added.

"We knew once we got Drop 2 completed it would be harder to fulfill our commitment," she said. "But we've had several rain events, and we've already sent the whole amount that the U.S. was required to send."

The water promised by environmental groups and Mexico will be sent to the wetland at a later date during the pilot run, she added.

Looking ahead

If the pilot run is successful, and Reclamation decides to bring the plant online full-time, environmentalists will watch closely to make sure the wetland is fully protected, Pitt said. "If they're going to continue to run the plant, there are a lot of issues to be examined," she said. "I think EDF and our conservation partners will be adamant about making sure the Cienega is protected in the future."

But the Yuma Desalting Plant's long-term cost-effectiveness remains largely unknown. Even if the pilot run at one-third capacity is a success, McCloskey said making the necessary improvements to allow the plant to operate at full capacity would be costly. For example, she said, all of the plant's piping would need to be replaced.

"There's a pretty big capital investment that would need to be made just to address the wear and tear and aging," she said. "I don't know where that money would come from, so that's a pretty big hurdle to wade through in terms of the plant's future."

Reese writes from Santa Fe, N.M.