At the time, PacifiCorp’s Condit Dam on Washington’s White
Salmon River was one of the largest dams to be removed in the United States.
Its removal that opened up 33 miles of new habitat for
salmon and steelhead spawning and rearing caused biologists to wonder if the
fish that had been extirpated from the river when the dam was built would or
They also wondered if the impact of removing the dam – it
was done with explosives punching a 16-foot hole in the dam and releasing an
immense amount of sediment – would ruin the 3 miles of habitat downstream of
the dam where Columbia River tule fall chinook spawned, the only salmonid
spawning in any numbers in the river prior to the dam’s removal October 26,
Two studies by the U.S. Geological Survey put those fears to
bed. One study shows that the lower portion of the river is actually restoring
itself faster than thought and that tule fall chinook are continuing to spawn
in the river’s lower reaches. Roughly 1,700 tule spawners are estimated to have
spawned in the White Salmon last fall.
“Salmon Habitat Assessment for Conservation Planning in the
Lower White Salmon River, Washington” was published in May 2015 (http://pubs.usgs.gov/of/2015/1100/pdf/ofr2015-1100.pdf).
The study area covers the lower six miles of the river, including three miles
that was downstream of the dam where tule fall chinook spawned and the three
miles of the former dam’s reservoir, known as Northwestern Lake.
“The lower White Salmon River continues to be used by salmon
for spawning and rearing downstream of the former Condit Dam site and salmon
and steelhead are using the newly accessible habitat upstream of the dam site
as well,” the May study says. “The general trend for the last 2 years of
spawning surveys was increasing numbers of returning Chinook salmon and
increasing redd locations.”
The second study, published November 4, 2015, and titled
“Effects of Dam Removal on Tule Fall Chinook Salmon Habitat in the White Salmon
River, Washington,” http://onlinelibrary.wiley.com/doi/10.1002/rra.2982/abstract
provides more information about how the White Salmon River is changing.
“As expected, dam breaching dramatically affected channel
morphology and spawning habitat due to a large load of sediment released from
Northwestern Lake,” the November study says. “Forty-two per cent of the project
area that was previously covered in water was converted into islands or new
shoreline, while a large pool near the mouth filled with sediments and a delta
formed at the mouth.”
While the pool area that was Northwestern Lake decreased
68.7 percent in the study area, glides and riffles – features most conducive to
spawning – increased 659 percent and 530 percent, respectively, the report
says. Spawning habitat increased by 46.2 percent after dam breaching due to an
increase in these glides and riffles.
Condit Dam since its construction in 1912-13 had blocked
passage to the river’s upper reaches, confining spawning to the lower 3.3 miles
of the river from its confluence with the Columbia River to the former dam.
Tule fall chinook salmon that have long frequented the lower
White Salmon are one of 13 Columbia basin stocks that are listed under the
federal Endangered Species Act. They are listed as threatened.
“Redd observations provided support that the study area is a
migratory corridor for salmon and steelhead and that the lowest 2–3 miles had
the highest concentration of documented fall Chinook salmon redds. The study
area has potential for restoration/conservation areas to improve/conserve
salmon habitat,” the May study concludes.
At the time it was breached, about 63.6 million cubic feet
of sediment had collected behind the dam. It was “abruptly breached with an
explosive blast with about a 16-ft-wide hole at the base of the dam that
rapidly emptied the reservoir and much of the sediment consisting mostly of
sand, silt, and clay,” according to the studies.
“The outflow of silt, sand, and gravel filled pools
throughout the lower river, created gravel bars, and a delta at the confluence
with the Columbia River,” the May study says.
It goes on to say that the river continues to change since
the dam was breeched and may continue to be in a state of flux for some years.
Natural processes are taking over, with large woody debris and gravel moving
into the river’s lower reaches. “The amount of time these watershed processed
take to reach equilibrium is unknown,” the study says.
A USGS survey in 2014 concluded that salmon habitat had
improved already at that time in the lowest one mile of river “due to increased
gravel recruitment, favorable velocities, and depths for spawning.” It also found that that lowest river mile was
still subject to some channel instability and the potential for gravel bars to
change if and when a larger flood event occurs.
The USGS generally found habitat conducive to salmon
spawning and rearing throughout the entire 6-mile study area. Still, areas
along the former Northwestern Lake lacked “a properly functioning riparian
corridor,” the May study says. However, revegetation projects by PacifiCorp and
Yakama Nation Fisheries were underway last year.
Spawning surveys in 2013 by the Washington Department of
Fish and Wildlife found spring and fall chinook spawning the mainstem river.
While most of the spawning was in the lower two miles of river, they did find
evidence of spawning in the area of the former lake and on the mainstem as far
upstream as the confluence of Buck Creek (river mile 4.9) and Rattlesnake rapid
(downstream of Husum Falls at river mile 7.6).
A 2014 survey found two to three times the number of spring
chinook spawners upstream of the former dam (216 spawners) with some seen in
Spring Creek at river mile 6.6. Tule fall chinook spawner abundance also was
higher, with just under 10 percent of the total number of spawning tules found
upstream below Steelhead Falls at river mile 2.6, according to the November
The Yakama Nation in 2014 found steelhead redds upstream of
the former Northwestern Lake in Buck and Rattlesnake Creeks. There is also
evidence that steelhead are spawning as far upstream as BZ Falls and Big
Brother Falls at river mile 15.5. Both are upstream of Husum Falls, “indicating
this is not a complete passage barrier for steelhead,” the May study says.
For more information on the 2014 spawning survey, see CBB,
February, 13, 2015, “Salmon, Steelhead Spawning, Rearing In New White Salmon
River Habitat Above Removed Condit Dam Site,” http://www.cbbulletin.com/433156.aspx
The dam was the only man-made impoundment between the
Cascade Mountains’ Mount Adams and the Columbia River and its removal opened
about 33 miles of new spawning and rearing grounds for steelhead and 15 miles
of new habitat for salmon in the White Salmon River basin.
The dam’s owner, PacifiCorp, agreed to decommission and
remove the project dam and water conveyance system in accordance with the 1999
Condit Hydroelectric Project Settlement Agreement and the related Federal
Energy Regulatory Commission Surrender Order issued in December 2010. The
private utility decided that it would be more economical to remove the dam than
it would be to outfit the dam with salmon passage facilities that would be
required by FERC to relicense the facility.
The White Salmon Working Group, which is a consortium of
Yakama Nation, federal, state, and PacifiCorp biologists, has estimated the
White Salmon River has enough spawning grounds to accommodate more than 600
steelhead spawners and 1,200 fall chinook. Bull trout, coho, lamprey and spring
chinook could also benefit from a reconnected river.
-- CBB, May 31, 2013, “A Year After Condit Dam Breaching,
Natural Origin Salmonids Spawn In New Miles Of Upstream Habitat” http://www.cbbulletin.com/426822.aspx