at Dworshak Dam in Idaho dropped flows over last weekend to help reduce the
prospect of local flooding downstream in the Clearwater River and further down
the Columbia River where water levels are at flood stage at Vancouver,
the same time and taking advantage of the lower flows, less spill and lower
total dissolved gas levels in the North Fork Clearwater River, hatchery
operators downstream of the dam released smolting juvenile spring chinook to
begin their migration to the ocean and are now releasing some steelhead smolts
a month earlier than normal.
March 16, the U.S. Army Corps of Engineers, which operates the dam, dropped
outflow from 22,500 cubic feet per second to 12.5 kcfs, lowering Clearwater
River water elevations by about one foot. Outflow at the dam had been at 22.5
kcfs since March 12 as the Corps had begun to reduce the surface elevation in
the dam’s reservoir – a flood control precaution – to make room for spring
to the reservoir are already high due to heavy precipitation and snow melt from
lower level mountains, peaking at 52.6 kcfs, according to the Corps.
Precipitation in the North Fork Clearwater River basin, where the dam is
located, was 214 percent of normal in February.
next day, March 17, the Corps dropped outflow from 12,500 cubic feet per second
to 7.5 kcfs for half a day and back up to 8 kcfs to reduce the chance of local
flooding, but also to create lower flow and TDG levels that would allow safe
conditions to release spring chinook smolts from hatcheries downstream.
the Corps is still aiming for an April 15 flood control elevation that could be
as low as 1,445 feet, an essentially empty reservoir if the April early bird
prediction of the basin’s water supply forecast of 3.17 million acre feet
persists in the coming week.
the lower outflow, the reservoir has been rising, not dropping to the flood
control target, Steve Hall, Water Program Manager for the Corps’ Walla Walla
District, told the interagency Technical Management Team at its conference call
Monday, March 20. The reservoir elevation was at 1,528.6 Monday, which is 36
feet higher than the end of month flood control target. It was under 1,510
have to move water,” Hall said. “We’re backed up against the wall with no other
place to go” but to release more water from the dam.
Corps increased outflow Monday afternoon by 2 kcfs per hour until it reached 25
kcfs later in the day.
Dworshak inflow and reservoir level predictions at https://www.nwrfc.noaa.gov/river/station/flowplot/flowplot.cgi?lid=DWRI1.
will not relieve flooding either locally or in the lower rivers, according to
the Corps’ Julie Ammon at TMT. There will still be a system flood emergency
throughout the Columbia and Snake rivers. Yet flows are dropping off, she said,
and all the Corps and Bureau of Reclamation storage projects, such as Dworshak
and Brownlee Reservoir on the Snake River, must begin spring system flood
said this latest push of water in the system is due to precipitation and low
level snow melt. It is not a part of the spring runoff. “We’re back to drafting
operations and preparing for the spring freshet,” she said.
the lower flows and much lower TDG levels created by spill at Dworshak Dam over
the weekend, the U.S. Fish and Wildlife Service and the Nez Perce Tribe
released spring chinook juveniles from the Dworshak and Clearwater hatcheries,
according to Jay Hesse of the Tribe.
the lower flows, TDG in the hatcheries had dropped to under 100 percent, said
Dave Swank of the Service at the TMT meeting. Degassing equipment at the
hatcheries lower dissolved gas levels of the river water used in hatcheries. That
compares with hatchery TDG levels of over 104 percent when Dworshak’s outflows
were at 22.5 kcfs and TDG at the dam exceeded 120 percent. At 7.5 kcfs, TDG at
the dam dropped to106 percent.
operation at Dworshak Dam is complicated because the dam’s largest generator is
being repaired. That generator accounts for more than half the generation.
Consequently, most of the outflow is through spill, not generators, resulting
in higher than acceptable TDG levels in the river and in the hatcheries
Water Act rules allow a TDG level of 110 percent. Elevated gas levels stirred
up by water plunging into dam tailraces can negatively affect fish and other
with the increase in flows Monday and a corresponding increase in dissolved gas
in the river and in the hatcheries, Swank said the hatcheries are planning an
early release of steelhead to move the fish out of the high TDG environment.
releases of 1.4 million steelhead at the Dworshak National Fish Hatchery began
Monday to remove the fish from the supersaturated conditions in the hatchery,
Swank said. The hatchery also released 1.6 million spring chinook Monday for
the same reason.
today, March 24, he said all steelhead at the Dworshak Hatchery will have been
released upstream in traditional release locations a month early, released
directly into the Middle Fork at the hatchery or moved into ponds at the
hatchery supplied by reservoir water to mitigate for high gas levels. The 1.1
million fish in the protected ponds will be released on schedule in mid-April
into the river at the hatchery.
if reservoir water blended with river water does not adequately reduce gas
saturation levels, these fish may need to be emergency released as well,” Swank
said. “Long-term survival of these fish and the wild fish in the river is hard
to estimate, given the early release timing and significant exposure to high
saturation levels in the hatchery and in the river system locally and downstream
said it took the collaboration of the Nez Perce Tribe, the Service and Idaho
Fish and Game “to get the fish released and avoid potentially catastrophic
the increase in flows from storage dams, flooding at Vancouver is predicted to
stay above minor flood stage (16 feet) at around 17 feet at least through this
week, according to the National Weather Service.
National Weather Service hydrograph of the Columbia River at Vancouver is at
flood stage at Vancouver is 20 feet and major flood stage is at 25 feet. The
highest crest was June 13, 1948 when the river reached a level of 31 feet. It
hit 27.2 feet February 9, 1996.
river levels are likely to stay with us through spring, according to a NOAA
spring outlook, which is predicting moderate flooding this spring over southern
Idaho in the Snake River basin. NOAA said Idaho this year had received its
second highest recorded snowfall.
snowmelt from rain storms on top of snowpack has already caused flooding at
lower elevations of this region. How long the flooding could last and how
intense it will be depends on future precipitation and temperatures,” a NOAA
news release said (http://www.noaa.gov/media-release/spring-outlook-risk-of-major-flooding-in-north-dakota-moderate-flooding-in-idaho).
in the region, the Columbia River InterTribal Fish Commission and the Oregon
Department of Forestry are predicting below average temperatures and above
average rainfall from April to June, while NOAA is predicting a more normal
snowpacks should generally peak at greater-than-average depths and slightly
later than usual,” according to Pete Parsons in a March 16 forecast -- https://www.oregon.gov/ODA/programs/NaturalResources/Documents/Weather/dlongrange.pdf
– meaning “cooler-than-average conditions should further delay the spring
will bring rain and more snow in the mountains and lower than average
temperatures. The month of May will bring below-average temperatures and
precipitation ranging from about 150 percent of average along the coast to
slightly below average across the eastern zones. Seasonal melting of mountain
snowpacks should be delayed, Parsons said. Cooler and wetter conditions will
continue into June.
meteorologist Kyle Dittmer released a similar spring forecast, predicting
slightly colder than average temperatures and higher rainfall. He predicted 105
percent of normal rainfall in April, 120 percent of normal in May and 110
percent of normal in June.
March 17, 2017, “Precipitation, Snowmelt Has River Operators Working To Control
Water Flow Through Mainstem Dams,” http://www.cbbulletin.com/438533.aspx.
CBB, March 10, 2017, “Dworshak Reservoir Emptied To Prepared For Snow Melt;
Snowpack Above Average Throughout Basin,” http://www.cbbulletin.com/438450.aspx