Yuma plant could deplete ecology of Sonoran wetland
StarNet online extra
See the Star's 2001 special report on the Colorado River delta, "Barely a
River," which includes a photo slide show. Go »»
By Mitch Tobin
ARIZONA DAILY STAR
The Yuma Desalting Plant, a $250 million facility stuck in mothballs since
it was completed a decade ago, may soon awaken and send its poisonous dregs
into the Sonoran Desert's largest wetland.
The 12,000-acre marsh - the Cienega de Santa Clara - is in Mexico's Colorado
River Delta. It offers a glimpse of the millions of acres of "milk-and-honey
wilderness" that famed ecologist Aldo Leopold visited in 1922, before
upstream dam-building reduced the Southwest's mightiest river to a trickle
and turned its delta into a wasteland.
Now, with a record drought depleting reservoirs along the Colorado, top
Interior Department officials have expressed interest in starting up the
Yuma plant so the United States can keep more water for its customers. Those
customers include Tucson, which is drawing an increasing amount from the
Colorado via the Central Arizona Project.
The 60-acre Yuma plant was built between 1975 and 1992 so the United States
could meet its treaty obligation to deliver river water to Mexico that's not
too salty. The plant was designed to use reverse osmosis to treat brackish
water flowing off cropland in Arizona's Wellton-Mohawk farming district,
returning the "desalted" water to the Colorado and sending the "reject
stream" of toxic brine through a parallel canal to Mexico.
But wet years in the 1990s meant the United States didn't need to use the
Yuma desalter. Instead, the United States sent the brackish water from
Wellton-Mohawk to Mexico in the canal that would have carried the brine. The
result was the continued blossoming of the Cienega de Santa Clara in a
sun-baked floodplain now 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 280 avian species, including the largest known
population of endangered Yuma clapper rails. The endangered desert pupfish
also lives in its olive waters.
The cienega has been receiving about 35 billion gallons each year from the
Wellton-Mohawk fields, about how much Tucson Water delivers to its
customers.
But if the Yuma plant were restarted, the cienega would get a third as much
water and it would be three times as saline, according to an Interior
Department draft proposal.
Should the plant come on line, the cienega's vegetation would disappear,
said Ed Glenn, a scientist with the University of Arizona's Environmental
Research Lab who has studied the area since 1991.
"It would become a repository for selenium-laden, poisonous water," he said.
Selenium is a naturally occurring metal that can hurt fish and birds by
accumulating in the food chain.