The U.S. Fish and Wildlife Service is renewing its insistence on a test spill of water from Libby Dam to see if the higher flows have any biological benefits for the threatened Kootenai River white sturgeon.

The state of Montana has consistently resisted releasing water over the dam's spillways on grounds that it produces gas levels in the river that far exceed the state's water-quality standards.

In April 2006, Gov. Brian Schweitzer's administration promised a lawsuit if federal agencies attempted to implement test spills at the dam, and the state has since engaged in litigation over the matter.

The conflict has persisted because a federal biological opinion for sturgeon recovery still calls for at least three test spills over a 10-year period. It comes down to a stalemate between the Endangered Species Act and the federal Clean Water Act, which Montana has adopted in its entirety.

Caught between the state and the service is the U.S. Army Corps of Engineers, the agency that operates Libby Dam.

Last week, Montana officials received correspondence from the Corps of Engineers once again raising the biological opinion's call for a 10,000 cubic-feet-per-second spill on top of the dam's powerhouse capacity release of 25,000 cfs.

"We recognize that a meaningful test of spill releases at Libby Dam would likely exceed Montana's total dissolved gas standard," wrote Col. Michael McCormick, district commander for the Corps of Engineers. "However, given the provisions of the 2006 USFWS BiOp and the steadily declining wild population of the Kootenai River white sturgeon, the Corps would like to work cooperatively with you to perform a scientifically sound spill test at Libby."

Cooperative management is not the issue, according to Brian Marotz, a Montana fisheries biologist who works as the state's liaison on Columbia Basin water management issues.

The problem, Marotz said, is that there are no provisions for waivers or other exceptions to the state's clean water standards and there is deep concern about long-term impacts from elevated gas levels on other fish in the river, including the threatened bull trout.

Even so, Marotz said, "the service is very serious about doing this year if possible."

Jason Flory, a Fish and Wildlife Service fisheries biologist who also is chairman of a committee in charge of sturgeon recovery, confirmed that a spill test to comply with the biological opinion is a priority.

"If the water year shapes up in a way that would allow us to spill and do it in a meaningful way, then we would want to see a spill," Flory said.

So far this year, snowpack measurements in the Kootenai basin are slightly above average. Spilling is not necessarily an option in a high-water year, Flory said, because Lake Koocanusa must then be drawn down for flood-control purposes, which can make less water available for a spill at the time it's needed.

"It's a unique set of stars that have to line up in the right way in order to get the conditions" for a spill, Flory said.

A spill test would be aimed at determining whether the higher flows prompt more adult sturgeon to swim upstream beyond Bonners Ferry, Idaho, into a stretch of cobble- and gravel-bottomed river that is suitable for spawning.

Spawning conditions are considered poor in the sand and silt riverbed below Bonners Ferry. If a test spill were conducted, the movements of adult spawners that are tagged with radio transmitters would be closely monitored.

Flory stressed that spill is not considered to be a "long-term solution."

Rather, any biological benefits that are measured from a spill test could help justify the installation of one or more additional turbines at Libby Dam to boost flows without increasing gas levels in the river.

But the Bonneville Power Administration and the Corps have raised concerns about the cost and the need for additional turbines.

"They have said they want to see a biological benefit," Flory said. "If we can demonstrate a biological benefit, that provides justification to looking to more reliable means in getting that water out."

Marotz questions whether the timing and "shape" of increased spring releases are more important than the sheer volume of the release.

Last year, spring flows were increased to mimic a natural spring freshet. Those flows fell far short of the 30,000 cfs that could result from a test spill, yet about half of the tagged adult sturgeon swam upstream past Bonners Ferry for spawning.

Marotz suggests that successful spawning may be attributed to a gradual decrease in flows after the spring peak -- something that may not be possible if there is an emphasis on simply releasing as much water as possible because of water availability in Lake Koocanusa.

"If Montana is unable to stop the spill test, we'll need funding and personnel to monitor the gas effects on Kootenai River biota," Marotz wrote in correspondence to other Montana officials.

Monitoring during a 2006 spill that was forced by an unusually rapid runoff found a high incidence of gas bubble trauma in fish below the dam, including 100 percent of sampled bull trout 11 days into the 14-day spill.

Symptoms of the trauma are actual bubbles that develop on the fish. The symptoms subside, but there is uncertainty about whether there are long-term impacts, such as reduced vision or harm to reproductive systems.

Ultimately, Marotz and Flory aren't sure how the statutory stalemate over spilling water at Libby Dam can be resolved.

"That's for the lawyers to answer," Flory said.

Bruce Measure, one of Montana's representatives on the Northwest Power and Conservation Council, said there are concerns that higher flows may actually degrade conditions in the river below the dam, and that limited funding may be better used for habitat restoration work that is being developed for the so-called "braided reach" section of river upstream from Bonners Ferry.

Last year, the state of Montana joined the Center for Biological Diversity in a lawsuit against federal agencies. While the state does not share the center's arguments, Measure said, it does have an interest in preventing spill at Libby Dam and other operations that would be harmful to Kootenai River fisheries.

All parties in the litigation recently agreed to a two-month extension to reach some form of settlement, or to agree on terms that would narrow the issues.