Libby Dam Water Spill May Encourage Sturgeon Spawning

Water from Lake Koocanusa in northwest Montana will soon start spilling over the top of the giant Libby hydroelectric dam – but on purpose.

From this AP story:
The latest effort to save North America’s largest freshwater fish from extinction begins this week when water is spilled over Montana’s Libby Dam to encourage the ancient fish to spawn for the first time in more than three decades. The wild Kootenai River white sturgeon, a toothless beast from the days of dinosaurs, has a large head, armor-like scales, can reach 19 feet long and top 1,000 pounds. It takes 20 or 30 years for white sturgeon to mature and reproduce. An isolated population of the bottom-feeding behemoths lives along a stretch of the Kootenai that passes through Montana, Idaho and British Columbia, Canada. The construction of Libby Dam in 1974 stopped the river from flooding Bonners Ferry, Idaho, but also prevented the high water flows that triggered the sturgeon to move upriver and spawn.

Before the dam, there were an estimated 10,000 Kootenai sturgeon. Fewer than 500 mature adults of spawning age remain. The effort this week will spill up to 10,000 cubic feet of water per second over the dam in a huge waterfall for up to seven days, in what scientists hope will push the sturgeon to more productive spawning grounds in Idaho. The water will spill from Koocanusa Reservoir into the Kootenai River, where scientists hope the sturgeon will swim to the Bonners Ferry area. The U.S. Army Corps of Engineers on Tuesday began sending more water through the dam’s turbines, in preparation for opening spill gates on Thursday. “The idea is to recreate more of the natural, spring conditions,” said Michael Milstein of the U.S. Bonneville Power Administration, which markets the power from the dam. “That is believed to be a factor that led sturgeon upriver to spawn.”