The Technical Management Team, charged with the difficult
task in a low water year of balancing spring juvenile fish passage with water
and power needs in the region, dropped McNary flow objectives for the second
week running and briefly raised flows from Dworshak Dam to help pass juvenile
chinook salmon through lower Snake River dams.
Balancing available water to sustainable river flows, TMT
again dropped spring flow expectations at McNary Dam for the second week in a
row from 180,000 cubic feet per second to 170 kcfs at a special meeting, May 4.
Then, at its regularly-scheduled meeting May 6, it raised
flows from Dworshak Dam on the North
Fork of the Clearwater River from 5 kcfs
to 9.7 kcfs (full powerhouse flows) in order to help struggling juvenile salmon
pass through lower Snake River dams. The Dworshak increase will also help flows
at McNary Dam.
As an additional aid to Snake River and Columbia River
flows, the Bureau of Reclamation said May 7, that it would gradually increase
flows out of its Milner Dam in the upper Snake River near Twin Falls, Idaho, to
2 kcfs by May 11 and maintain that flow through early June. The upper Snake
River reservoirs are at 83 percent of storage capacity.
BOR says it is taking this action to provide additional
water for salmon migration lower in the rivers “in accordance with NOAA
Fisheries 2008 Upper Snake Biological Opinion.”
Faced with one of the worst water supply forecasts in the
past 55 years, TMT lowered the flow objective at McNary Dam from 220 kcfs to
180 kcfs on May 1, hoping that flow level would be enough to help juvenile
salmon pass the dam and other Columbia River dams downstream.
Average flows at McNary the week of April 27 were at 160
kcfs, so to reach the 180 target set by TMT on May 1 required dam operators to
increase their draft of the Grand Coulee reservoir.
By Monday, May 4, it had become apparent to the managers
that Coulee was drafting at a much faster pace than they had anticipated,
risking the chance that Lake Roosevelt, the dam’s reservoir, would not refill
by early summer.
“The inflow at Coulee is running about 85,000 cubic feet per
second and the Snake River is done with runoff,” said Tony Norris of the
Bonneville Power Administration. “None of that adds up to 180 kcfs at McNary
The 85 kcfs inflow includes about 10 kcfs that will be
pumped into Banks Lake to be used for irrigation, so the Coulee inflow is
really closer to 95 kcfs, he added, but the Banks Lake allotment is not
available to augment flows downstream.
Passing inflows through Coulee, Norris said, gives McNary
about 160 kcfs to 165 kcfs. “What we are doing now will use up at least
one-half foot per day,” he warned, speaking of the 180 kcfs target.
Given the situation, TMT on Monday further reduced average
flows at McNary to 170 kcfs and, by Wednesday this week, flows were averaging
165 kcfs to 170 kcfs, according to Mary Mellema of the BOR, which operates
Grand Coulee Dam.
She said flows will continue at this level as long as the
Coulee reservoir does not fall below an elevation of 1,243 feet. An elevation
below that would cause difficulties in refilling the reservoir and that’s water
that will be needed throughout the summer. The reservoir elevation on Monday
was 1,249.1 feet, she said, but “by the end of Wednesday it would be at 1,247
feet, with only four feet to play with,” if outflows continued at 180 cfs.
Refill begins after May 13.
The federal biological opinion for Columbia/Snake salmon and
steelhead includes a flow objective at McNary Dam of 220 kcfs to 260 kcfs
during the spring juvenile salmon migration season, which is achievable during
most years. However, in low water years, the BiOp allows for flexibility in
managing the situation.
For more information, see CBB, May 1, 2015, “As Water Supply
Expectations Lower So Do Flow Targets At McNary Dam During Juvenile Salmon
The current flows of 165 kcfs to 170 kcfs at McNary seems to
be working for juvenile salmon as they are passing down through the Columbia
River at an expected rate, according to Paul Wagner, NOAA Fisheries, at TMT’s
May 6 meeting.
However, passage of juveniles on the Snake River are below
expectations and some steelhead juveniles are likely being waylaid in the Lower
Granite reservoir, Wagner said as he pushed for increasing flows from Dworshak
Dam on the Clearwater River, upstream of Lower Granite Dam.
Steve Hall of the U.S. Army Corps of Engineers, which
operates the project, warned that using Dworshak water now could jeopardize refilling the
reservoir by the end of June. In fact,
given the changing water supply forecast in the area, he said it would be more
prudent to aim to refill the reservoir in early June.
Runoff volume April 1 was 70 percent of normal and that
dropped to 54 percent of normal by May 1, he said.
“The difference is the weather,” Hall said. “It’s a
relatively cool protracted melt and that doesn’t translate into runoff. The
forecast is for 10 kcfs inflow, but it more likely will peak at 8 to 8.5 kcfs.”
Water from Dworshak can be used in the mid-summer months of
July and August to cool flows at lower Snake River dams.
“What’s more important, refill or flow augmentation at this
point in time?” he asked.
TMT’s salmon managers chose a short period of flow
augmentation to try to move more juvenile salmon through the lower Snake River,
asking for four days of full powerhouse flow, which is about 9.5 kcfs, going to
5 kcfs Saturday and down to 1.6 kcfs Sunday, where flows will stay while the
“None of this is where people want to go and we acknowledge
the significant risks this operation has on refill,” Wagner said, speaking for
salmon managers at the May 6, TMT meeting. “But we think the benefits to the
spring fish will outweigh the temperature benefit later on.
“We’re going into this with eyes wide open,” he added. “But
the water we could potentially use in August, we’ll use now for these smolts.”
TMT will continue to consider both the McNary and the
Dworshak decisions again at its meeting, May 13.