Threat of flooding high
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| 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.
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