The U.S. Army Corps of Engineers has ramped up flows from Libby Dam even higher to prevent Lake Koocanusa from topping full pool, but the higher flows continue to cause flooding downstream at Bonners Ferry, Idaho.

The dam has been releasing water at powerhouse capacity of 25,000 cubic per second. Adding in flows from the spillway and sluice gates raised the total outflow from 40,000 cfs to 46,000 cfs between Wednesday and Thursday. 

Water is flowing into Lake Koocanusa at the rate of 75,000 cfs for most of the week because of record rainfall in the Kootenai Basin.

The reservoir has been rising by 1 to 1.5 feet per day and it is expected to continue doing so, with potential to reach full pool elevation of 2,459 feet by Saturday.

“Once the final storage space behind Libby Dam is diminished, we will be forced to pass inflows to keep the reservoir from overfilling,” said Kevin Schaffer, a water manager for the Corps’ Seattle District. “Raising outflows last night will slow the reservoir fill rate and allow river flows upstream and downstream of the dam to recede further before the remaining space in the reservoir is exhausted.”

The Kootenai River elevation at Bonners Ferry was 1,766 feet, more than two feet above flood stage, and it could reach as high as 1,768 feet, according to the Corps, which predicts the river could remain above flood stage until mid-July.

A Corps response team has been assisting Boundary County and Bonners Ferry city officials. Around 300 “super sack” sandbags were deployed along 500 feet of a levee that protects the Kootenai River Inn Casino and Spa. 

“There are no signs of any levees being breached,” said Tina Wilson, an acting public information officer for Boundary County. “In the low-lying ground behind the levees, there is ground seepage. That’s not unusual when the river is high.”

Some homes are surrounded by water, Wilson said, and some private roads are no longer passable.

During flooding in 2006, when there was a similar spill emergency at Libby Dam, there was hundreds of thousands of dollars in damages, mostly to agricultural lands behind the levees. No monetary damage estimates have been calculated yet, Wilson said.

Record rainfall has soaked the basin in June. At Bonners Ferry, total precipitation for the month so far has been 5.2 inches, more than 300 percent of the June average of 1.66 inches. The previous record at Bonners Ferry was 3.96 inches in 1981.