Army Corps deploys flood team, operates Libby Dam to reduce flood damage
by U.S. Army Corps of Engineers – Libby Dam
June 26, 2012
As the current storm system continues adding widespread rainfall to the Kootenai River Basin, which is already exceeding precipitation records for the month of June, the U.S. Army Corps of Engineers has deployed a flood team to the basin and is providing technical assistance to Lincoln County, Mont. and Boundary County, Idaho.
The storm is forecast to add 0.5-1.5 inches of precipitation to the basin over a 24-hour period starting today before drying out later in the week. The additional rainfall is on top of record precipitation as measured at Bonners Ferry, Idaho. Current precipitation for the month of June is 4.39 inches, more than 260 percent of the June average which is 1.66 inches. The previous June record for precipitation at Bonners Ferry was set in 1981 when it was measured at 3.96 inches.
Current inflow at Libby Dam is approximately 75,000 cubic feet per second and outflow is 40,000 cfs. Elevation at Koocanusa Reservoir is 2,453.7 feet and it has been rising 1-1.5 feet per day during the past six days. The reservoir is expected to continue rising by about one foot per day through the end of the month and could reach 2,458 feet, or within one foot of full pool, by June 30. Total June inflow volume at the western Montana dam is approximately 3.3 million acre feet; the third highest volume in the past 50 years.
The Corps is operating Libby Dam to reduce flood damage, modifying outflows to keep the reservoir refill rate manageable while simultaneously maintaining elevation at Bonners Ferry, Idaho, as low as possible. The river at Bonners Ferry will remain above the flood stage of 1,764 feet as a result of high tributary inflows, precipitation and dam outflows. The current elevation at Bonners Ferry is 1,764.8 feet. The amount of actual precipitation from the current rainstorm will determine the next steps for flood operations at Libby Dam.
Intense June rainfall in the Kootenai Basin has also resulted in a high water level on Kootenay Lake, downstream of Libby Dam. The current elevation at Queens Bay is 1,753.0 feet, the highest level since 1974. Libby Dam operations are being managed to provide flood risk reduction for both the Canadian and U.S. portions of the Kootenai Basin.
The Corps’ emergency operations center and reservoir control center are continually monitoring conditions. Additional volunteer flood fight team members and reservoir managers at the Corps’ Seattle District remain on alert and poised to respond as necessary to areas affected by flooding.
Residents and businesses in the river basin should be prepared for potential flooding. The National Weather Service and downstream communities have plans in place to promptly alert potentially affected people about the situation and what action to take. Citizens are encouraged to contact local emergency managers and work with them to determine the best path to prepare for potential flooding.
Libby Dam - U.S. Army Corps of Engineers – Libby Dam