Chum salmon have yet to be seen near Ives
Island and both the river flow and tailwater elevation at Bonneville Dam remain
low, but salmon managers and dam operators this week set next Tuesday, November
7, as the start to annual chum flows at the dam.
The interagency Technical Management Team at
its meeting Wednesday, November 1, unanimously set in motion an annual
operation at the dam that will protect spawning chum, listed as threatened
under the federal Endangered Species Act.
The operation generally begins November 1, but
at its meeting last week TMT put the operation off by a week due to low flows
and no chum.
On the morning TMT made the decision this
week, the flow at Bonneville Dam was 84,100 cubic feet per second and the
tailwater elevation was at 8.7 feet
Initial chum operations require a tailwater elevation at the dam of at least
11.5 feet and no more than 13 feet, an elevation range that encourages arriving
chum to spawn and to protect the chum redds once they’re established.
Even with the current rainfall, that tailwater
elevation requirement likely will require the U.S. Army Corps of Engineers to
begin releasing more water from Bonneville.
“We need to proceed no later than Tuesday to
start with the expectation that precipitation will catch up and so will the
fish,” said Paul Wagner of NOAA Fisheries.
Annual chum operations ensure that enough
water will flow over chum redds, or nests, near Ives Island downstream of
Bonneville Dam to protect the fertilized eggs until they emerge next spring. So
the operations seeks flows high enough to protect chum as they build their
redds, but not so high that chum would be encouraged to spawn in areas that
could be dewatered when flows drop.
Although chum have yet to begin making nests
in the Hamilton Creek area downstream of Bonneville Dam, there is enough water
in the creek and at Hamilton Springs that chum could begin spawning there even
without a higher tailwater, said Scott Bettin of BPA. Bettin and other TMT
members toured the spawning area Friday, October 27.
Some four chum have crossed Bonneville as of
October 31, according to the Fish Passage Center (www.fpc.org).
The weather forecast out 8 to 10 days calls
for a 70 to 80 percent probability of lower than normal temperatures throughout
the Columbia River basin and a 30 to 50 percent probability of higher than
normal precipitation. The early April – August runoff forecast at The Dalles
Dam is 93 million acre feet, about 107 percent of normal, said Doug Baus of the
TMT’s coordinated chum operations that it used
in 2016-17 follows a tiered approach that largely depends on the amount of
water passing the dam and the Corps’ ability to maintain a tailwater elevation
that is best for spawning chum and incubating eggs. Initially, the Corps will
operate project outflow to maintain the tailwater elevation between 11.5 and 13
feet during all hours. As river flows increase, chum operations adjust to
protect the salmon.
For information on chum operations guidelines,
see CBB, October 27, 2017, “Operations For Spawning ESA-Listed Chum Delayed;
Early Basin Water Supply Forecast Normal,” http://www.cbbulletin.com/439785.aspx
--CBB, January 6, 2017, “ESA-Listed Chum
Salmon Below Bonneville Dam Show Good Spawning Rate; Flows Maintained To Cover