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Sturgeon spills to run through June 16
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June 13, 2012 |
After a five-day interruption for flood risk
management, the U.S. Army Corps of Engineers
re-commenced spilling as part of the sturgeon
flow augmentation at Libby Dam on June 10 and
expect the operation to last through Saturday.
The sturgeon flow augmentation operation began
on June 4, but the spill operation was halted
when heavy rainfall, increased tributary inflows
and high Kootenay Lake elevation caused the
Kootenai River to rise swiftly and reach flood
stage, 1,764 feet above mean sea level, at
Bonners Ferry, Idaho. The spill operation
resumed June 10 and could include spilling up to
10,000 cubic feet per second above full
powerhouse capacity, approximately 26,000 cfs,
increasing outflows to about 36,000 cfs for a
total of seven non-continuous days.
Spill amounts will be based upon the river stage
at Bonners Ferry, which the Corps is targeting
to maintain between 1,762.5-1,764 feet elevation
during the sturgeon flow operation.
In addition, with upper basin snowpack still
higher than normal and the current inflow
forecast at 123 percent of average, the Corps
continues to closely monitor local conditions
and will make flow adjustments as necessary for
flood risk management. The Corps plans to
release flows of 26,000 cfs for the foreseeable
future and possibly continue to spill up to
2,000 cfs after Saturday. The operation after
Saturday is intended to maintain enough space
behind Libby Dam to accommodate potentially high
inflows to the Dam through early July.
Biologists and water managers will monitor the
spill operation, called for in the 2006 U.S.
Fish and Wildlife Service (USFWS) Biological
Opinion, as clarified in 2008, to test whether
additional flows over the spillway will provide
the habitat conditions thought to be necessary
for successful sturgeon spawning. Total
dissolved gas levels will be monitored by the
Corps to ensure they do not exceed criteria
established by the Montana Department of
Environmental Quality. Montana Fish, Wildlife
and Parks will continue monitoring fish for
symptoms of gas bubble trauma.
The flow augmentation operation is part of a
collaborative, ongoing effort by regional
biologists to enhance spawning and migration
conditions for sturgeon in the Kootenai River
near Bonners Ferry. Increased flows are intended
to provide river conditions that may foster
sturgeon spawning, successful egg hatching, and
survival of larval sturgeon in the reach of
river upstream of Bonners Ferry, where sturgeon
do not currently spawn successfully. While
hatchery reproduction has increased the number
of young sturgeon in the river, federal, state,
and tribal partners hope to improve habitat
conditions for adult sturgeon to successfully
reproduce on their own.
The U.S. Army Corps of Engineers' primary
consideration in operating Libby Dam is to
minimize risk to human life, health, and safety,
while meeting the dam's multiple purposes and
responsibilities. The dam is a multi-purpose
water resource developed for flood risk
management, hydropower, fish and wildlife, and
recreation. |
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