one point last spring, the level of court-mandated spring spill designed to aid
downstream passage of juvenile salmon stalled the passage of adult salmon at
Little Goose Dam on the lower Snake River.
fix, according to the interagency Technical Management Team at its meeting in
late May 2018, was to balance spill for juvenile salmon with reduced spill to
encourage spring chinook salmon “lost” in the Lower Monumental Dam pool
downstream to move up and pass Little Goose Dam.
problem in both 2017 and 2018 was a disparity between the number of fish
passing Lower Monumental and those expected to pass the next dam upstream,
Little Goose Dam, and the culprit was too much spill. In fact, there were about
6,000 to 7,000 fewer fish than expected at Little Goose, Doug Baus of the U.S.
Army Corps of Engineers told TMT at its year-end review of river operations
was one of four speakers addressing the issue of Little Goose Dam in the
day-long session and was among four speakers covering the lessons learned from
the altered operations at the dam. Others included Eryck Van Dyke of the Oregon
Department of Fish and Wildlife, Daniel Deng of the Pacific Northwest National
Laboratories and Paul Wagner of NOAA Fisheries.
is made up of fisheries and hydro/reservoir managers from state, federal and
tribal agencies. Every December the group looks back at actions taken during
spring and summer in managing Columbia and Snake river federal hydro/fish
additional spring spill to state TDG limits, known as gas caps, was mandated at
lower Columbia and Snake river dams by an April 2017 order from Judge Michael
H. Simon of the U.S. District Court of Oregon. Simon had ordered 24-hour spring
spill for one year, 2018 only, beginning April 3 at lower Snake River projects
and April 10 at lower Columbia River projects, and ending June 20 on the Snake
River and June 15 on the Columbia River.
disparity in counts from one dam to the next upriver dam is why from May 30
through June 3 TMT changed operations at Little Goose to encourage the lost
fish to move up into the dam’s fish ladders.
CBB, June 1, 2018, “River Managers Make Spill Changes To Improve Spring Chinook
Adult Passage In Lower Snake,” http://www.cbbulletin.com/440846.aspx.)
was a complicated operation for several days that combined a reduction in
daytime spill at Ice Harbor to encourage adult spring chinook to move to the
dam’s fish ladders, along with a higher operating pool upstream to accommodate
the reduced river flow through the dam, and then returning to the higher spill
later in the day.
had to be taken when reducing spill because without spill juveniles can find
their way past dams through the powerhouse and, according to Baus’
presentation, “Each juvenile powerhouse encounter reduces subsequent SAR by a
relative 9-13 percent.”
operation, which was also employed during spring spill in 2017, was to drop the
spill level at the dam from 45 percent to 30 percent of the river from 4 am to
noon, store the remaining inflow in the Little Goose pool above the 1 foot
minimum operating pool (MOP) range of 633 feet to 634 feet as needed, depending
noon to 4 pm, spill was increased to pass the river’s inflow. From 4 pm to 4
am, spill was increased as needed to draft the Little Goose pool back to MOP
while remaining under 130 percent total dissolved gas, which was a spill level
of about 125,000 cubic feet per second. The TDG level of 130 percent is higher
than that allowed by Washington and Oregon state standards of 125 percent.
the operation saw 26 hours when the pool level was above MOP, Baus said, adding
that the experimental operation, which was in effect from May 30 to June 3, was
spill was reduced, we saw more adults at the fish ladder,” researcher Deng told
TMT at its review meeting.
a study of 2018 fish passage at Little Goose, Deng and his associates found
that adult fish prefer to enter the fish ladder during the daytime. Of 400
acoustic-tagged fish that made it to Little Goose, some 95.26 percent entered
the fish ladder between 4 am and 7 pm.
May 21 to 25 when the spill level at the dam was 35 to 40 percent of the river
spilled, 30 to 50 percent of adults in the tailrace entered the fish ladder,
and when spill was at 45 percent of the river May 25 – 29, just 20 percent of
adults in the tailrace entered the fish ladder, Deng said.
TMT ordered less daytime spill and spill was dropped to 30 percent, 40 to 65
percent of adults in the tailrace entered the fish ladder, and more of those
fish entered the North Shore fish ladder than did at the South Shore fish ladder,
in his presentation, said that in “the event there is the delay of adult chinook
salmon in periods of high spill in 2019 going to 30 percent spill in a more
timely manner and storing above MOP would likely reduce the delay of adult chinook
salmon in the LGS tailrace.”
to Wagner, spill at Little Goose to 45 percent of the river began by court
order in 2005 and as “it got to early summer, the fish slowed down.” The fish
between Lower Monumental and Little Goose should pass the upper dam within 3
addition, more fish experienced fallback during 2018 (9.8 percent) compared to
the 2008 (3.9 percent) and 2013 (7.5 percent) studies, Baus said in his
and Deng’s presentations are at http://pweb.crohms.org/tmt/agendas/2018/1219_Agenda.html
CBB, July 27, 2018, “Court-Ordered Spill Completed In June; Corps Sends Judge
Last Of Three Reports Detailing Operations,” http://www.cbbulletin.com/441186.aspx
CBB, June 8, 2018, “NOAA Fisheries Delivers First Court-Ordered Spring Spill
For Fish Report; Shows Complex Operations,” http://www.cbbulletin.com/440890.aspx
CBB, June 15, 2018, “Fish/River Managers Have Differing Interpretations On What
‘Spill To The Gas Cap’ Looks Like,” http://www.cbbulletin.com/440945.aspx
May 18, 2018, “Court-Ordered Spring Spill Now Moot As High Columbia/Snake Flows
Forcing Involuntary Spill At Dams,” http://www.cbbulletin.com/440765.aspx
April 13, 2018, “Court Ordered Spring Spill For Fish Begins On Four Lower
Columbia River Dams,” http://www.cbbulletin.com/440516.aspx
CBB, April 6, 2018, “New Court-Ordered Spill Regime Based On Dissolved Gas Caps
Begins This Week,” http://www.cbbulletin.com/440479.aspx