Threat of flooding high |
| 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. On Monday, Boundary County Emegency Management Director Dave Kramer and Incident Commander Bob Graham alerted Boundary County Commissioners of the heightened potential for flood risk, and set in place measures to minimize potential damage and to alert county residents if danger becomes imminent. The county sent out letters to property owners earlier this year, and hopes are that the warnings were taken seriously. "With the weather the way it's been, this is shaping up to be a troublesome year," Graham said. 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 p.m. * May 12 at Libby City Hall, Libby, Mont., at 7 p.m. |