Muddy Creek is nondescript, a narrow stream trickling through the sagebrush steppe of southern Wyoming. But like many Western waterways, it carries selenium, a natural poison that seeps from rocks and dirt and accumulates in the food chain much as mercury does.
Both humans and animals need tiny amounts for good health, but too much is dangerous. In areas with a lot of selenium in the soil, including Utah's Middle Green River Basin and Nevada's Stillwater National Wildlife Refuge, activities that bring soil into contact with water -- irrigating, mining, drilling and road building -- boost natural concentrations, and can cause illness and deformities in people, livestock and wildlife.
Now, researchers are studying the Muddy Creek watershed, trying to determine how much of the element occurs naturally, and how much is being released by human activity. Tracking selenium sources in this way is tricky, but essential; few studies have examined where selenium comes from and where it ends up.
JoAnn Holloway, a physical scientist with the U.S. Geological Survey, and her team of researchers have tested for selenium in water, soil, rocks and invertebrates in this part of the Colorado River's upper tributaries for several years. The team has set baseline data for the region, measuring background levels and investigating whether recent local natural gas development is increasing amounts, as erosion from newly scraped roads and well pads washes selenium into streams. By studying the watershed now, prior to extensive development, Holloway's team may help land managers ward off potential problems. "Selenium is going to become an issue (as energy development continues)," says Holloway. "Our study was a way of saying, ‘We need to keep our heads up about this.' "
The USGS, the Bureau of Land Management and the U.S. Fish and Wildlife Service all watch for selenium pollution in various ways, but no agency has clear responsibility for comprehensive West-wide monitoring. The Environmental Protection Agency has regulated levels in drinking water since the 1970s, but has yet to develop rules limiting significant sources, such as coal ash produced by coal-fired power plants.
For years, selenium was often overlooked as an environmental problem. Then, in the early 1970s at Kesterson Reservoir in California's San Joaquin Valley, a Bureau of Reclamation project began dumping irrigation water, carrying selenium leached from farm fields into wetlands. By the early 1980s, fish, birds and reptiles were failing to hatch or had serious deformities –– missing eyes, misshapen beaks, protruding brains. "That's a sort of worst-case scenario of how nasty selenium can get," Holloway says. Irrigation is still a major source of selenium pollution in Western waterways.
It made hair-raising headlines again this February. Photographs of deformed trout, some two-headed, surfaced from a study commissioned by the J.R. Simplot Company, which wants to release selenium at levels above national and state standards at its southeastern Idaho phosphate mine. The U.S. Fish and Wildlife Service concluded that Simplot's report systematically underestimated the impact on wildlife. (The company's request is still pending.)
The reproductive abilities of native fish such as razorback suckers and Colorado pikeminnow are already limited by selenium in the Colorado River watershed. After hatching, the poorly developed offspring are likely to sicken or be eaten. "These are fish that evolved to live in these waters," says Ken Leib, a hydrologist for the USGS. "Current selenium levels are probably higher than they were historically."
But quantifying selenium increase at a single location isn't easy. Selenium levels vary seasonally and annually, depending on water flows, and data on historical background amounts are thin to nonexistent. Distinguishing natural levels from development-caused ones is, says Holloway, "kind of a dicey operation." It's easier to study contaminants that don't occur naturally, such as pesticides or dyes.
At Muddy Creek, Holloway's team found no clear uptick in selenium concentrations in developed versus undeveloped areas. That may be due to the relatively short monitoring period. However, the team did find that the creek's aquatic and riparian invertebrates -- damselfly larvae and long-jawed spiders -- are accumulating more selenium than is considered safe for the birds and fish that feed on them. This link, demonstrating how water quality affects selenium levels in the food web, is the study's key finding, says Patrick Lionberger, a fisheries biologist at the Rawlins BLM field office.
While it's too early to say how the study might affect energy development permitting, Lionberger says it does give the BLM more to consider in the approval process. If a strong link between selenium concentrations and energy development is established, state and federal regulatory agencies might decide to change land management practices. The BLM won't comment on possible changes, but Holloway's study implies that they might potentially include some limits on road and well-pad building; the state could potentially restrict surface discharge of the water produced by drilling.
For now, reluctantly, Holloway's USGS team has had to quit gathering data -- they ran out of funding. But even as research proceeds in fits and starts, the West's selenium issues are likely to become more severe. "The big issue here in Muddy Creek and in the West in general," says Travis Schmidt, an invertebrate ecologist on Holloway's team, "will be, I think, the cumulative effect. We're changing the way we use land, and there is no big effort to monitor the effects of selenium on downstream resources. Over the total landscape that could be a huge problem for wildlife."