The once-wild West has been tamed by the hand of the farmer - thanks to the federal government's web of water projects stretching across this arid land. But is the water that nourishes crops also wreaking havoc on the West's wildlife? In an effort to find out, scientists are collecting water samples, sediments, fish, and waterfowl on nine Western wildlife refuges, to be sent to government laboratories for testing.
There is not yet enough data to determine if agricultural drainwater - sometimes containing toxic levels of elements such as selenium and boron - is poisoning the habitat of wildlife across the West, researchers say.
But many environmentalists say they believe there is already convincing evidence of damage. They point to the Kesterson Wildlife Refuge in central California, where selenium-laced irrigation water has been blamed for deformities and deaths of birds, fish, and other animals.
Is Kesterson an isolated case, as government agencies, farmers, and wildlife enthusiasts are hoping? Or is it a precursor of future problems for the West, as some environmentalists suggest?
Certainly, experts say, potential for trouble exists. About half of the United States - from Texas to the Dakotas, and west to California - is a semi-arid area dotted with ancient deposits of selenium. This naturally occurring element is also found in the East, but there the soil is acidic. In the alkaline soil of the West, selenium is soluable - and can become mobile in the environment.
``In the West, where much of the area only gets a couple inches of rain a year, there wasn't much of a [selenium] problem until federal irrigation projects brought huge amounts of fresh water to the land,'' says Zach Willey, an economist in the Western regional office of the Environmental Defense Fund.
Leached from the land during irrigation, selenium is transported in the drainwater, which in turn feeds into rivers, lakes, the ocean, or wetlands used as wildlife refuges. In some cases, Mr. Willey says, selenium is likely to build up to toxic levels, as it did at Kesterson.
Just over a year ago, the US Interior Department identified 19 sites in 13 Western states that could have contaminant problems stemming from agricultural drainwater, says John Deason, the department's irrigation drainage coordinator. A preliminary survey found high levels of selenium at the sites, but it did not confirm the same deadly effects on wildlife that were discovered at Kesterson in 1984.
An Interior task force - including teams of hydrologists from the US Geological Survey, biologists from the Fish and Wildlife Service, and engineers from the Bureau of Reclamation - last May began monitoring water quality and its impact on wildlife at nine of the refuges.
Seven of the nine studies are expected to be completed by the end of the year.
The task force has not compiled enough data to determine if other Kestersons are in the making, Dr. Deason says. ``I don't mean to hide behind this statement, but it is very complicated.''
He says variables such as rainfall, the presence of other trace elements in the water, waterfowl diet, and the type of species at the refuges make each site unique.
Even so, the manager at the Stillwater Wildlife Management Area sees signs that something is wrong on the northwest Nevada site, which collects waste water from federal irrigation projects.
Dead birds were discovered at Stillwater last year, and the site experienced ``large fish die-offs last year and again this year,'' says Ron Anglin of the US Fish and Wildlife Service.
Mr. Anglin speculates that the fish die-offs may be natural occurrences, whereas the dead birds are ``definitely unusual.''
But he is quick to note that, while the birds contained high levels of some elements, ``nobody is saying for sure they died from selenium.''
The picture is complicated, he says, because water here also contains mercury from turn-of-the-century mining upstream. It contains high levels of boron and arsenic, too, he adds.
``We know that something here is not quite normal, but we can't find a cause,'' Anglin adds.
Scientists have known for decades that selenium is toxic in large amounts, says Thomas H. Jukes, a professor of biophysics at the University of California, Berkeley. But it is also an essential element for nutrition, he says. Dr. Jukes, who has been studying the element for 30 years, says he believes the selenium found in the vegetables grown in California's fertile San Joaquin Valley is beneficial.
Selenium provides a perfect lesson on comparative toxicity, Jukes adds. ``It's the theory that everything is poisonous and nothing is poisonous,'' he says. ``The dose alone is what determines the poison.''