High water could help sturgeon
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| May 27, 2011 |
SEATTLE - While the U.S. Army Corps of Engineers
continues to regulate Libby Dam for flood risk
management, conditions are such that many
attributes for a previously planned sturgeon
spill are likely to be achieved without the
spill.
 The
2008 Libby Dam Biological Opinion Settlement
Agreement requires the Corps to conduct a late
spring "spill test" to determine if additional
Kootenai river flows will cause changes in the
sturgeon's migration and spawning behavior. It
is hoped that increased flow will ultimately
coax Kootenai sturgeon to migrate to, and spawn
over, rocky substrates that exist upstream of
Bonners Ferry.
However, since current record-high water
supplies in the Kootenai River basin are likely
to increase flows beyond what had been planned
for with a "spill test," discharges in addition
to powerhouse flows from Libby Dam may not be
necessary. The U.S. Fish and Wildlife Service is
working with the Corps and
others to monitor the effects on endangered
Kootenai River white sturgeon.
Unusually high snowpack, as much as 80 percent
above average in some areas of the Kootenai
River basin, combined with forecasted
precipitation, have increased the risk of
flooding downstream of the dam in Libby.
To mitigate potential flooding from swift
snowpack runoff, the Corps is regulating
discharges from the dam to maintain the Kootenai
River at or below flood stage elevation of 1,764
feet at Bonners Ferry, beginning May 28. By
keeping the river at or near flood stage in
June, Koocanusa Reservoir will have more space
available for late season snowmelt or rain
inflows.
Inflows to the dam are approximately 50,000
cubic feet per second and discharges are 16,000
cfs. Inflows are predicted to increase to more
than 90,000 cfs in the coming days. This weekend
releases will increase to approximately 23,000
cfs.
Koocanusa Reservoir is currently refilling at a
rate of two to three feet per day, which is
expected to continue at least through mid-June.
However, if inflow rates spike from increased
snowmelt, the reservoir could rise as much as
six to eight feet per day as more inflows are
held behind the dam to prevent flooding
downstream.
The Corps' primary consideration in operating
Libby Dam is minimizing risk to human life,
health and safety, while meeting the project's
multiple purposes. Flood risk management
operations at the dam always take precedence
over sturgeon operations.
Residents and businesses in the river basin
should continue to be prepared for potential
flooding as snowpack begins to melt. As 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. |
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