Corps increases releases from Libby Dam to create storage space
by U.S. Army Corps of Engineers – Libby Dam
May 2, 2011
To increase water storage space behind Libby Dam, in anticipation of potentially swift snowpack runoff, the U.S. Army Corps of Engineers ramped up releases from the dam by discharging an additional 5,000 cubic feet per second through the dam's sluice gates Saturday morning.
This action is creating more storage in the Koocanusa Reservoir and will allow the Corps to retain more Kootenai River flow behind Libby Dam. Meanwhile the downstream unregulated tributaries, which are forecasted to flood due to unusually high snowpack, can pass more of their spring snowmelt and rain flows with less potential to threaten Bonners Ferry.
Current high-elevation snowpack is 128 percent of normal and lower-elevation snowpack is 153 percent in the Kootenai River basin. The National Oceanic and Atmospheric Administration forecast is for cooler than normal temperatures through June with continued higher than normal precipitation through May.
When warmer temperatures cause snowpack to melt rapidly, Kootenai River flows may be at or above flood stage. In addition, downstream tributaries to the Kootenai which are not controlled by Libby Dam, such as the Yaak, Moyie and Fisher Rivers, are likewise expected to be at or above flood stage. Increased releases from Libby are intended to keep up with these anticipated high inflows.
Libby Dam powerhouse releases are currently 16,400 cubic feet per second. The additional discharges through the sluice gates ramps up releases to 21,400 cfs, amassing more reservoir storage for expected unusually high peak runoff from snowpack.
"Each day the snowpack doesn't melt increases the likelihood of a more dramatic runoff because it will be compressed into a smaller timeframe - pushing more water into the system at a rapid rate - and raising the Kootenai and unregulated tributaries to flood stage level in a short period of time," said Col. Anthony Wright, Commander, U.S. Army Corps of Engineers, Seattle District.
While it is uncertain the extent of effects on the fish population, increasing levels of total dissolved gases may have some impact. The Corps and Montana Department of Environmental Quality are closely monitoring the total dissolved gas level in the river below Libby Dam.
Residents and businesses in the river basin should be prepared for potential flooding once snowpack begins to melt. Should flows approach flood stage, 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.
The Corps is regulating Libby Dam for flood risk management, closely monitoring weather conditions, snowpack readings and inflows to mitigate flood risk downstream.
Public information meetings for Libby Dam operations are scheduled for:
May 9 at the Kootenai River Inn, Bonners Ferry, Idaho, at 7:00 p.m.
May 12 at Libby City Hall, Libby, Montana, at 7:00 p.m.
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