Lake Koocanusa will be allowed to rise two feet above the normal maximum level in the latest effort to limit downstream flooding.
The Army Corps of Engineers, which operates Libby Dam, announced Tuesday that it reached an agreement with BC Hydro to store additional water in Koocanusa up to an elevation of 2,461 feet.
The normal maximum elevation of Koocanusa is 2,459 feet.
The reservoir has been rising about half a foot per day over the past several days despite high releases of water from Libby Dam.
Libby Dam water releases were increased from 46,000 to 48,000 cubic feet per second on Monday night.
Inflow into Koocanusa was 60,000 cubic feet per second.
On Tuesday the Kootenai River below Libby Dam was flowing at just above flood stage of 27.5 feet, while farther downstream the river level at Bonners Ferry, Idaho, was at 66.4 feet.
Flood stage is 64 feet.
The high water has caused a variety of flooding problems in the Bonners Ferry area.
“This coordination to allow up to two feet above the normal maximum will enable the Corps to maintain a lower release from Libby Dam than would otherwise be required,” the Corps said in a press release. “It is estimated that this may reduce the river stage for the Kootenai River at Bonners Ferry by as much as 0.4 feet.”
The emergency water measures follow record rainfall in the Kootenai River Basin.
At Bonners Ferry, June precipitation totaled 5.24 inches, more than 315 percent of the June average of 1.66 inches. The previous June record for precipitation at Bonners Ferry was 3.96 inches in 1981.
Libby Dam received 4.34 inches of rain in June.
In the Flathead Valley, most flooding risks have subsided even though July began on a rainy note following a record wet June.
The Flathead River, after topping flood stage last week, was running more than three feet below flood stage on Tuesday afternoon.
The Whitefish River also has dropped below flood stage.
June’s rainfall of 6.2 inches (as measured at Glacier Park International Airport) made it the single wettest month on record for the Kalispell area.
Other places around the valley had even higher rainfall, according to the National Weather Service:
Location June Precip.
West Glacier 7.90
Hungry Horse 7.75
Libby Dam 4.34