The Tucson, Ariz.-based Center for Biological Diversity and Moab-based Living Rivers notified the two federal agencies, and the Department of Interior, on Tuesday, citing what they call violations of the Endangered Species Act.

The two groups are leaning heavily on a report released last month by the U.S. Geological Survey, which concluded that efforts since 1991 to restore the Colorado River below the dam to something resembling its original state "have not produced the hoped for restoration and maintenance" of endangered fish species, such as the federally protected humpback chub.

In fact, the study says, three of the original eight native fish species - including the roundtail chub, bonytail chub and Colorado pikeminnow - have been eliminated from the Colorado River in Glen Canyon and the Grand Canyon, while the humpback chub population has declined between 30 percent and 60 percent.

"We've been waiting patiently for 11 years," said Robin Silver, board chairman of the Center for Biological Diversity. "We think this is a pretty comprehensive study which shows that the Colorado River in the Grand Canyon is being destroyed, and that the Glen Canyon Dam adaptive management plan has been a failure."

Bureau of Reclamation spokesman Barry Wirth declined comment, citing the pending litigation.

Congress passed the Grand Canyon Protection Act in 1992 to reverse the decline of the native fish species. The Glen Canyon Dam adaptive management plan was adopted in 1995 to guide the bureau in implementing recovery guidelines set by the Fish and Wildlife Service.

The focus of those efforts have been a series of flow test experiments that were designed to push more sediment downstream in a bid to create sandbars and backwaters that serve as habitat for the fish. But those tests have largely failed to deliver the desired results.

Overall, "research and monitoring have conclusively demonstrated a net loss of fine sediment from the Colorado River ecosystem," the study said. "Closure of Glen Canyon dam eliminated about 84 percent of the sand that historically entered the Grand Canyon."

The geological survey report also identified positive signs. Warmer water coming out of Lake Powell, depleted because of the drought, has - combined with a program to eliminate non-native fish - helped increase the number of juvenile humpback chubs, though their long-term fate is unclear. And the most recent flow test, conducted a year ago, succeeded in pushing sediment downstream and creating sandbars in isolated areas.

But the two environmental groups call it too little, too late.

"They issued some hope," Silver said of the study, "But the 10 thousand-pound gorilla is that they're showing progress when the flows are naturally low. Without the drought, I don't think they could say they've been successful."

jbaird@sltrib.com