Seasonal flow augmentation for Kootenai River white sturgeon gets underway at Libby Dam

May 23, 2015

from the Columbia Basin Bulletin http://www.cbbulletin.com/default.aspx Flow augmentation for Kootenai River white sturgeon got underway last Friday, May 22, at Libby Dam after U.S. Army Corps of Engineers water managers, along with federal, tribal, and state fishery biologists, have determined that water temperatures and flows are sufficient for the operations to begin. Releases from Libby Dam were increased to full powerhouse capacity of about 26,500 cubic feet per second, and they will remain at that level for about a week before decreasing to about 20,000 cfs for four to five days. This year’s flow augmentation for sturgeon does not include releasing additional volumes of water over the dam’s spillway, and it will involve a single peak in flows. In past years, flow augmentation has involved spill and more than a single peak in flows. The augmentation operation is part of a collaborative, ongoing effort to enhance migration and spawning conditions for sturgeon in the Kootenai River near Bonners Ferry. Increased flows are intended to provide river conditions that will improve the chances of adult sturgeon reaching a stretch of river upstream from Bonners Ferry with habitat thought to be conducive to successful spawning, egg hatching and survival of larval sturgeon. The Kootenai Tribe of Idaho has a sturgeon hatchery program that has steadily increased the number of young sturgeon in the river since 1992, but the numbers of wild adult sturgeon capable of spawning have been dwindling over time. The sturgeon flow augmentation operation requires a volume of water to be released from Libby Dam based on water supply forecasts for Lake Koocanusa. The forecasted inflow volume for the April-to-August period is 5.4 million acre feet, about 92 percent of average, and that sets this year’s sturgeon volume at .80 million acre feet. Citing recent runoff models, the Corps states there is “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.” In past years, sturgeon flows have had a part in the Kootenai River reaching or exceeding flood stage at Bonners Ferry. The Corps will be monitoring river conditions at Bonners Ferry during flow augmentation, and operations will be adjusted with the aim of staying below the local flood stage.