Environmentalists and water officials unveiled a plan Monday to restart a desalination plant in Yuma without harming a valuable marsh in Mexico's Colorado River Delta.
The desalter, built at a cost of some $250 million, has been in mothballs for a dozen years. Drought has led many U.S. water users to advocate bringing the plant back to life so that Lake Mead won't be further drained to meet treaty obligations with Mexico.

Doing so, however, threatened to destroy the 40,000-acre Cienega de Santa Clara since its water supply would likely be slashed. What water did arrive would be a toxic stream of brine coming from the desalter.

The plan, which needs state and federal approval, calls for:

* Pumping groundwater from waterlogged areas near Yuma to provide an alternate supply

* Improving agricultural conservation and fallowing cropland, either voluntarily or with payments to farmers

* Using the desalter to provide water to cities and businesses on either side of the border.

The plan was drafted by four conservation groups and officials from the Central Arizona Project, Arizona Department of Water Resources, city of Yuma and Bureau of Reclamation.

The 60-acre Yuma plant was built between 1975 and 1992 so the United States could meet its obligation to deliver river water to Mexico that's not too salty. It was designed to use reverse osmosis to treat brackish water flowing off Arizona's Wellton-Mohawk farming district, returning the cleaner water to the Colorado and sending the reject stream of brine to Mexico in a canal parallel to the river.

But wet years in the early 1990s meant the United States didn't need to operate the desalter. Instead, runoff from Wellton-Mohawk was sent to Mexico in the canal meant for the brine. The result was the blossoming of the cienega in a sun-baked flood plain dominated by sterile salt flats.

Biologists say the cienega declared a biosphere reserve by Mexico in 1993 has become a vital stopover for birds traveling the "Pacific Flyway." It provides habitat for more than 95 bird species, including the endangered Yuma clapper rail.

A 1944 treaty requires the United States to send Mexico about 10 percent of the Colorado's average flow. But the United States has not received credit for the brackish water it sends to the cienega. That has forced officials to drain some 35 billion gallons each year from Lake Mead and deliver it to Mexico enough water to supply about three-quarters of Tucson Water's customers.

* Contact reporter Mitch Tobin at 573-4185 or mtobin@azstarnet.com.


Publication date: 2005-05-03