Wetland vies for Colorado River’s water

On the Colorado River Delta, some 250 miles west southwest of Tucson as the crow flies, sits Cienega de Santa Clara.

It’s a 63-square-mile patch of wetland – a key stop for migrating birds along an arid stretch of the Pacific flyway. It’s the largest remaining wetland on the Colorado River Delta and part of an internationally recognized conservation area.

It also sits squarely in the center of a debate over a multimillion-dollar water desalting plant just west of Yuma, Ariz., which is slated for a trial run later this year. Salty wastewater from the plant would flow down a drainage system that currently feeds Cienega de Santa Clara, essentially dooming the wetland, environmentalists say.

Proponents of the trial argue that the freshwater the plant would provide is sorely needed for the region’s cities and farms.

The debate highlights the challenge of slaking the thirst of a growing population that draws on the already-oversubscribed Colorado River, while protecting the region’s ecological gems. The challenge is expected to grow more acute if global warming dries out the region further, as many climate models project.

If, however, other sources of water for the wetlands can be found, particularly if the water comes from sources on both sides of the US-Mexican border, it would represent “a tremendous breakthrough,” says Karl Flessa, a paleobiologist at the University of Arizona who studies the river’s historical ecosystems.

Sitting in his office beneath a pair of enlarged satellite photos of the delta, Dr. Flessa explains that such an outcome would represent the first time US water managers had allocated Colorado River water specifically for environmental purposes outside the Grand Canyon. It would also represent the first time water had been delivered across the border for environmental uses.

Why the wetlands expanded
Getting there, however, is the hard part.

The wetland’s water is brackish residue from farmland east of Yuma. Once, that water was channeled back into the Colorado and into Mexico. But in the 1970s, the US agreed to improve the quality of Colorado River water Mexico receives. The quickest way to attack that problem was to divert the water – and it ended up in Cienega de Santa Clara. The influx of water stimulated the wetland’s expansion from a few hundred acres in 1977 to more than 40,000 acres of marshland – a patchwork of open water and expanses of cattails.

Meanwhile, the US Bureau of Reclamation was pursuing a high-tech approach – building the Yuma Desalting Plant. The idea: Run the brackish farm water through the plant and return it to the river. But for technical and budget reasons, the plant is not on line full time.

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