SEATTLE – Water managers at the U.S. Army Corps of Engineers, along with federal, tribal, and state fishery biologists, have determined that water temperature and flow are now sufficient to commence sturgeon flow augmentation operations at Libby Dam, Montana, for endangered Kootenai River white sturgeon downstream in Idaho.
While this year’s flow augmentation for sturgeon does not include spilling additional volume over the dam, plans include increasing flows to full powerhouse capacity for about a week, and will only include a single peak.
Sturgeon flow augmentation will begin this Friday, May 22, at 7:00 a.m. Flows will be increased to full powerhouse capacity, approximately 26,500 cubic feet per second, and will remain at that level for about one week before decreasing to 20,000 cfs for four to five days. The post-peak operation to guide the flow shape of the remaining sturgeon volume will be coordinated through the interagency Flow Plan Implementation Team.
The sturgeon flow augmentation operation is part of a collaborative, ongoing effort by regional biologists to enhance spawning and migration conditions for sturgeon in the Kootenai River near Bonners Ferry, Idaho. Increased flows are intended to provide river conditions that may increase sturgeon migration to the reach of river upstream of Bonners Ferry in habitat thought to be conducive to successful spawning, egg hatching, and survival of larval sturgeon While the Kootenai Tribe of Idaho’s conservation aquaculture program has steadily increased the number of young sturgeon in the river since 1992, the Tribe has collaborated with federal and state partners in recent years to construct instream habitat upstream of Bonners Ferry intended to provide conditions that may allow adult sturgeon to successfully reproduce naturally.
The sturgeon flow augmentation operation requires a volume of water to be released from Libby Dam based on the May water supply forecast for Lake Koocanusa. The forecasted inflow volume for the April to August period is 5.4 million-acre-feet (or 92 percent of average), which sets this year’s sturgeon volume at 0.80 million-acre-feet.
The latest model projections indicate a low chance of exceeding flood stage (1,764 feet above sea level) at Bonners Ferry, Idaho. Although June precipitation may increase flood risk from downstream tributaries to the Kootenai River not controlled by the dam, current snowpack data do not indicate a likelihood that flood stage will be reached or exceeded.
Libby Dam flow and stage projections are based on National Weather Service ensemble forecasts and are updated frequently during runoff season as weather and conditions change. Forecast modeling includes information on elevations, outflow, and Bonners Ferry seasonal elevation and peak height for the year. To see the latest projections, visit: http://1.usa.gov/1kP1lSH.
The U.S. Army Corps of Engineers' primary consideration in operating Libby Dam is to minimize risk to human life, health, and safety, while meeting the dam’s multiple purposes and responsibilities. The Corps will closely monitor Kootenai River elevation in Bonners Ferry during the sturgeon flow augmentation and will adjust operations with the aim of staying below 1,764 feet, the local flood stage.
A public information meeting for Libby Dam operations is scheduled for May 28 at the Kootenai River Inn, Bonners Ferry, Idaho, from 7-9 p.m.