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Seasonal flow augmentation for Kootenai River
white sturgeon gets underway at Libby Dam |
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May 23, 2015 |
from the Columbia Basin Bulletin
http://www.cbbulletin.com/default.aspx
Flow augmentation for Kootenai River white
sturgeon got underway last Friday, May 22, at
Libby Dam after U.S. Army Corps of Engineers
water managers, along with federal, tribal, and
state fishery biologists, have determined that
water temperatures and flows are sufficient for
the operations to begin.
Releases from Libby Dam were increased to full
powerhouse capacity of about 26,500 cubic feet
per second, and they will remain at that level
for about a week before decreasing to about
20,000 cfs for four to five days.
This year’s flow augmentation for sturgeon does
not include releasing additional volumes of
water over the dam’s spillway, and it will
involve a single peak in flows. In past years,
flow augmentation has involved spill and more
than a single peak in flows.
The augmentation operation is part of a
collaborative, ongoing effort to enhance
migration and spawning conditions for sturgeon
in the Kootenai River near Bonners Ferry.
Increased flows are intended to provide river
conditions that will improve the chances of
adult sturgeon reaching a stretch of river
upstream from Bonners Ferry with habitat thought
to be conducive to successful spawning, egg
hatching and survival of larval sturgeon.
The Kootenai Tribe of Idaho has a sturgeon
hatchery program that has steadily increased the
number of young sturgeon in the river since
1992, but the numbers of wild adult sturgeon
capable of spawning have been dwindling over
time.
The sturgeon flow augmentation operation
requires a volume of water to be released from
Libby Dam based on water supply forecasts for
Lake Koocanusa. The forecasted inflow volume for
the April-to-August period is 5.4 million acre
feet, about 92 percent of average, and that sets
this year’s sturgeon volume at .80 million acre
feet.
Citing recent runoff models, the Corps states
there is “a low chance of exceeding flood stage
(1,764 feet above sea level) at Bonners Ferry,
Idaho. Although June precipitation may increase
flood risk from downstream tributaries to the
Kootenai River not controlled by the dam,
current snowpack data do not indicate a
likelihood that flood stage will be reached or
exceeded.”
In past years, sturgeon flows have had a part in
the Kootenai River reaching or exceeding flood
stage at Bonners Ferry. The Corps will be
monitoring river conditions at Bonners Ferry
during flow augmentation, and operations will be
adjusted with the aim of staying below the local
flood stage.
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