Koocanusa Reservoir expected to remain low this summer

Seattle District, U.S. Army Corps of Engineers
Published June 27, 2019

In one of the driest years recorded for the 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.

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.

Water supply in the Kootenai basin has been very low all winter and spring:

  • Basin snowpack averaged about 70 percent of normal all winter
  • In February 2019, inflow into Lake Koocanusa was the lowest monthly inflow volume ever measured (between 1960-2019)
  • May precipitation was 36 percent of normal
  • June precipitation has been 45 percent of normal, thus far

The Corps’ swim platform at Souse Gulch will likely not be available for use because of low lake levels and access to private docks and marinas may be impacted.

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.

Scott Lawrence

Release no. 19-026