With climate change, Northwest rivers are
warming earlier and staying warm longer and that sometimes causes adult salmon
and steelhead migrating from the ocean to die in rivers before they can spawn,
often before they can even reach their spawning grounds.
Cold water refuges – small pockets of cooler
water, most located where tributaries meet mainstem rivers – along the Columbia
and Snake river migration corridor can briefly provide the respite fish need to
cool down and prepare for the remainder of their journey.
It’s the same as people finding shade or air
conditioning when it’s hot, Matt Keefer told members of the Northwest Power and
Conservation Council Fish and Wildlife Committee at the Council’s meeting
Keefer, a research scientist at the Department
of Fish and Wildlife Sciences at the University of Idaho, along with NOAA
Fisheries, federal Environmental Protections Agency and Oregon Department of
Environmental Quality scientists, have been searching the Columbia and Snake
rivers and their tributaries since 1996 to identify and understand where cold
water refuges are and how salmon and steelhead use them.
Research shows that salmon and steelhead find
cold water refuges along the migration journey, according to a Council blog,
and “sometimes hundreds or thousands of fish crowd into a single block of cool
In fact, when water in the Bonneville Dam
reservoir reaches 20 degrees Celsius (68 degrees Fahrenheit), some 60 to 75
percent of steelhead will find and stay in a cold water refuge along the dam’s
pool, according to Keefer.
The length of time a fish stays in the cool
water depends on their biological clock: steelhead, for example, generally will
not spawn until spring after their entry to the mainstem Columbia River and so
have the leisure to hang out and will stay for days or weeks in one refuge.
However, chinook and sockeye will only stay
from a few hours to a median of three days because they are motivated to be on
the spawning grounds much sooner. When river temperatures are at their highest,
fall chinook migration rates can drop by as much as 50 percent, Keefer said.
“The fish are very effective at locating
differences in temperature,” Keefer said. “Most of those are where tributaries
enter the mainstem rivers.”
He said the EPA has put together a primer on
how to find cold water refuges and so far has identified 191 sites in the lower
and mid-Columbia River and Snake River where the water temperature is 4, 5 and
even 6 degrees Celsius cooler (about 8, 10 and 12 degrees Fahrenheit) in August
than mainstem temperatures.
“As you go upstream of the John Day Dam and
further up into the Clearwater River, however, there are fewer refuge sites,”
“Primer for Identifying Cold-Water Refuges to
Protect and Restore Thermal Diversity In Riverine Landscapes,” published by the
EPA, can be found at https://www3.epa.gov/region10/pdf/water/torgersen_etal_2012_cold_water_refuges.pdf
Adult salmon and steelhead move quickly when
water is cool, but tend to slow and use refuges when the water warms. They
easily find refuges because they tend to migrate along the edges of mainstem
rivers, so the potential to encounter a cold water refuge is quite high, Keefer
A classic example of a cold water refuge in
the Bonneville Dam pool is Drano Lake in Washington’s Little White Salmon River
(river kilometer 261 - mile 162), where
the fish are drawn to the lake’s cool plume.
“Systems (such as Drano Lake) are highly
variable, complex thermal habitats,” Keefer said. “We know fish use these
plumes extensively to find cooler water, but winds in the area can also
disperse the plume” and fish will miss the cue.
But fishermen have learned about the refuge
and fish it extensively. “The fish go from the frying pan into the fire, so
it’s not all good,” he added.
On the other side of the Columbia River in
Oregon, the Hood River (rkm 273 – mile 170) is a limited use refuge because the
river has a shallow delta with debris that warms the water.
On the other hand, moving upstream, the
Deschutes River in Oregon (rkm 328 – mile 204) has a large cold water plume
that extends several kilometers downriver. Both fall chinook and steelhead will
move up the Deschutes River as far as Shearers Falls, 70 rkm upstream (43.5
However, with the selective water withdrawal
tower used by Portland General Electric in Lake Billie Chinook to attract
juvenile salmon and steelhead, warmer water is flowing down the Deschutes River
and the temperature differential between the Columbia River and Deschutes River
is not as great as it once was, Keefer said.
Other refuges are the relatively large refuge
at Wind River (rkm 249- mile 155) in Washington and a smaller refuge at Herman
Creek (rkm 243 – mile 151) used by both chinook salmon and steelhead.
At 18 degrees C (64.4 degrees F), steelhead
seldom leave the mainstem, Keefer said. But above that temperature they too
begin to look for refuges.
“Steelhead are very flexible in terms of migration,”
he said. “They have the luxury of time since they don’t spawn until the next
spring and their time in the refuge can last for weeks.”
Chinook salmon, however, tend to stay in the
river more than steelhead, Keefer said, and they move quickly until the river
temperature reaches 21 degrees C (70 degrees F). Then about 40 percent of the
chinook will stop briefly in a refuge.
“They do not have the luxury of time. If they stay too long (in a cool water
refuge), they may miss spawning,” he said.
Both sockeye salmon and coho salmon will
essentially stop migrating when water temperature reaches 21 degrees C, Keefer
said, and, at the higher temperature they will produce a lower quality egg.
Sockeye salmon are in the most hurry.
“In 2015, we know they moved into the
Deschutes and Drano Lake, but we’re pretty sure they just moved in to die,”
Keefer said of last year’s extreme river temperatures that killed 90 percent of
the Snake River sockeye before they reached Ice Harbor Dam. Snake River sockeye
are listed as endangered under the federal Endangered Species Act.
The Northwest can expect increasing water
temperatures as the entire Columbia River Basin will continue to warm.
“Currently, long stretches of the Columbia
River upstream of John Day Dam and the Snake River have no or very limited cold
water refuges,” Keefer said. “These reaches may present significant migration
barriers for adult fish and will have consequences for some fish populations.
Some of the barriers are episodic; some are likely to become chronic.”
The expectation is that the number of
preferred thermal habitats fish now use will be reduced as the climate warms
and the region needs to identify and protect what high quality habitat is now
The EPA inventory of refuges from the Pacific
into the Snake River is a great step, he added, but there are other critical
areas in the basin that need to be studied.
“If we know where refuges are and how they are
used, we can learn how to protect them,” Keefer said. That could involve, for
example, breaching dikes so that cold water reaches the mainstem river.
Tributary habitat can be shaded by planting trees, bushes and grasses along the
banks, and this may help cool the water. Cold water releases from storage
reservoirs can provide a limited benefit, but it dissipates as the water moves
--CBB, July 15, 2016, “Klamath River Study:
Cold Water Refuges Also Function As Disease Refuges For Juvenile Salmon,” http://www.cbbulletin.com/437131.aspx