Koocanusa expected to remain low this summer
In one of the driest years recorded for the Kootenay/Kootenai River Basin, extremely low spring precipitation combined with well below average winter snowpack and runoff will keep Lake Koocanusa significantly lower than normal this summer, the U.S. Army Corp. of Engineers reported June 27.
Reservoir elevation is projected to peak between 2,432 to 2,437 feet – potentially as much as 22 feet below the typical targeted peak pool elevation of 2,454 feet – and expected to occur in the first two weeks of August rather than late July.
“It has been a dry year overall,” said Logan Osgood-Zimmerman, U.S. Army Corps of Engineers’ upper Columbia River senior water manager. “We kept the reservoir nearly five feet higher at the end of December than in most years and then have been operating on minimum flows for much of winter and spring to try and conserve water.”
Currently, Lake Koocanusa is on track to have the fourth lowest inflow volume since 1960, the USACE said in a media release.
Water supply in the basin has been low all winter and spring, it added, noting the Basin snowpack averaged about 70% of normal all winter. In February, inflow into Lake Koocanusa was the lowest monthly inflow volume ever measured (between 1960-2019).
Additionally, May precipitation was 36%of normal and June precipitation was 45% of normal, as of June 27.
Libby Dam discharge gradually decreased from 20,000 cubic feet per second to 7,000 cfs from June 20-25 and is expected to remain at that level through August before reducing to 6,000 cfs in September.
Lead image: Cutts Marina along Koocanusa Reservoir as of Sunday, June 30. Carrie Schafer and Ian Cobb/e-KNOW photos