Koocanusa has reached 2,454 feet in elevation, just five feet below full pool, after the heavy rainfall of late June.
Information released by the U.S. Army Corps of Engineers last week said that Koocanusa saw very high inflows during the rainfall event.
The reservoir that contains water from the Kootenay River and Elk River before it flows through Libby Dam, Montana, saw 94,000 cubic feet a second of water coming into it on Friday, June 21. By Thursday, June 27, it had dropped to 50,000 cubic feet a second coming in. That is still high: by comparison, on Friday, June 7, 36,000 cubic feet a second was coming in.
To cope with the massive amount of water reaching the reservoir, engineers maxed out the amount of water going through Libby Dam to 25,000 cubic feet a second. Over the weekend of June 22 to 24, another 3,000 cubic feet a second was spilled over the top of the dam.
"Discharge will continue at elevated levels until flows have dropped and we are able to pass inflow," said the Army Corps' Adam Price in an operations update.
However, the huge amount of water going through Libby Dam is not causing problems downstream, according to Price.
"Kootenay Lake is seasonally low, and the stage at Bonners Ferry is expected to stay several feet below flood stage," reads the update.
Koocanusa was not expected to be as full as 2,454 feet this summer. In May, BC Hydro and the Army Corps said that the reservoir was forecast to reach 2,453 at the end of July, and stay at that level until September.
The large volume of water flowing into the reservoir is bringing debris that could hamper recreational users of Koocanusa.
Diane Tammen, BC Hydro’s East Kootenay community relations manager, said that BC Hydro is taking steps to reduce the debris flowing into Koocanusa.
“Due to the recent weather events and high water levels there is significant large woody debris which has come down the Elk River. This large debris is being collected behind a boom BC Hydro has recently constructed across the Elk River three kilometres downstream of the (Grasmere) bridge. The boom and the debris collection pens already in place help keep the debris off of the reservoir. We are in the process of acquiring additional boom sticks to increase storage capacity for collection,” said Tammen.
Each year BC Hydro spends about $100,000 on debris removal in Koocanusa.
“Since it’s early in the season, we have this year’s funding available. We will continue with the work and assess the situation as the season progresses,” said Tammen.