Although the count varies by day, as many as
137 chum salmon were counted on one day in late October downstream of
Bonneville Dam where they are expected to build redds (nests) and spawn during
November and into December.
The early arrival of chum, listed as
threatened under the federal Endangered Species Act, led to the request from
fisheries managers and the decision this week by the interagency Technical
Management Team to begin the annual chum operations that will continue through
the next five months, transitioning to chum incubation flows in late December.
Chum operations at the dam began today,
Friday, Nov. 2, at 6 am. The operations will maintain the dam’s tailwater
elevation at 11.5 feet so that the fish can move into spawning areas near
Hamilton Creek and Ives Island.
The chum were counted in late October, but
tailwater levels at the time were under 10 feet and much of the spawning area
that will be available to them as of today was unusable due to shallow water.
Some 60 chum were counted by Washington Department of Fish and Wildlife
biologists Oct. 22 and the biologists saw 137 chum Oct. 25. Three chum have
passed over Bonneville Dam.
Annual chum operations ensure that enough
water will flow over chum redds to protect the redds and fertilized eggs until
they emerge in spring. Initial spawning operations seek flows high enough to
protect chum as they build their redds, but not so high that chum would have
been encouraged to spawn in areas that could be dewatered when flows drop.
Last year, TMT began chum operations Nov. 7.
Due to the early arrival of the chum, operations this year are beginning one
TMT met for an unscheduled conference call
Monday, Oct. 29, to consider an early start to the chum operations. At that
time, flows at Bonneville were just 98,000 cubic feet per second, but rain over
the next 10 days, according to Doug Baus of the U.S. Army Corps of Engineers,
should bring flows up to about 128 kcfs.
The Northwest River Forecast Center had
forecasted Bonneville Dam flows today to hit about 123 kcfs and predicts flows
will rise to about 133 kcfs by Nov. 5 (see https://www.nwrfc.noaa.gov/river/station/flowplot/flowplot.cgi?id=BONO3),
but that’s without initiating the chum operations.
With local rain, flows by Tuesday had risen to
about 103 kcfs, with a tailwater elevation of 9.4 feet. Baus said precipitation
over the 10-day period will be 110 to 175 percent of normal in southwest
Washington and Northwest Oregon, with three-quarters to 1-1/4 inches expected
into this weekend alone.
More than two weeks ago when TMT last met to
discuss chum operations, the outlook was much different as the river operating
group was looking at a continued dry fall (see CBB, October 12, 2018,
“Providing Water Cover For ESA-Listed Chum Salmon Redds Below Bonneville Dam
Could Be Tough This Year,” http://www.cbbulletin.com/441644.aspx).
Flows were at 91.3 kcfs with a tailwater elevation of 8.7 feet as of Oct. 8.
TMT wondered if a significant amount of flow augmentation would be needed from
the Grand Coulee Dam’s Lake Roosevelt.
“Two things have changed” over the last two
weeks, Baus said. “The weather forecast and the arrival of the chum,”
explaining why TMT was meeting to consider an early start to chum operations.
To raise the tailwater level up to 11.5 feet
may take some additional water from Grand Coulee, but with the rain this week,
it is likely that less than one foot of the reservoir level will be needed to
augment chum flows, according to Scott Bettin of the Bonneville Power
Chum operations began at 6 am this morning.
The Corps will maintain a tailwater elevation of 11.5 to 13 feet. Actual flow
at the dam at 6 am this morning was 146.5 kcfs and the tailwater elevation was
at 12.1 feet.
As flows rise, TMT has adopted tiered guidance
for the operation:
If flows rise and if necessary, the tailwater
can go to 16.5 feet during the night (5 pm to 6 am), concentrating the highest
elevation around midnight.
With even higher flows, the tailwater can rise
to 18.5 feet during the night.
“Then, if increasing river flow precludes the
ability to manage tailwater within the steps above, operate to provide a
tailwater in the range of 13 to 16.5 feet during the day (6 am to 5 pm) and up
to the maximum within project 24-hour ramp rate limits during the night,” the
coordinated chum operations for 2017/18 says
Once started, TMT will continue flows and
tailwater elevation to protect the chum redds into mid- to late December and
then transition to similar flows to protect the redds through incubation.
--CBB, January 19, 2018, “Agencies Identify
Spawning Areas For Chum, Confirm Safe Water Levels Over Redds,” http://www.cbbulletin.com/440103.aspx