An environmental group that once called for the removal of Libby Dam announced Tuesday it will sue the government to get changes at the dam.

The Center for Biological Diversity wants the U.S. Army Corps of Engineers to release more water from behind the northwestern Montana dam in spring. Biologists have said that would help Kootenai River white sturgeon, which were added to the federal endangered species list in 1994.

Researchers say sturgeon have not successfully spawned in the river since the mid-1970s, when the dam was completed.

Among other things, high water could help clear out some of the sediment that hampers spawning. The change could help other struggling fish, including burbot and bull trout.

Higher spring flows on the Kootenai are included in a controversial federal proposal called "Var-Q." ("Var" is short for variable and "Q" is an engineering symbol for discharge.) The proposal worries some downstream landowners who fear more frequent floods.

Var-Q also worries landowners at Lake Roosevelt in Eastern Washington, where the government may mandate slightly lower water levels during some springs to make up for reduced flood capacity at Libby. Those concerns are being weighed by the corps and other agencies working on an environmental impact statement. A draft document is due by the end of the year with a final decision in 2004.

The Arizona-based Center for Biological Diversity contends the change should already have been made.

The corps' "continued foot-dragging" violates the Endangered Species Act, which forbids federal agencies from harming listed species, said Noah Greenwald, a Montana biologist for the environmental group, which filed the required 60-day notice of lawsuit Tuesday.

Corps spokesman Dave Harris said agency lawyers hadn't yet seen the notice, so couldn't comment.

Last year, the Center for Biological Diversity requested that the U.S. Fish and Wildlife Service order the dam breached to restore sturgeon. Two Montana groups -- the Ecology Center and the Alliance for the Wild Rockies -- joined that plea.

"We still support breaching the dam," but think Var-Q should be tried first, Greenwald said.