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Identifying, Preserving Columbia/Snake Cold Water Refuges Important Salmon Recovery Tool by Staff Columbia Basin Bulletin, August 26, 2016

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.

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 August 9.

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 water."

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," he said.

"Primer for Identifying Cold-Water Refuges to Protect and Restore Thermal Diversity In Riverine Landscapes," published by the EPA, can be found at 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 said.

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 miles).

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 available.

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 downstream.

Related Pages:
First Snake River Sockeye Reaches Sawtooth Basin by Staff, Columbia Basin Bulletin, 7/31/15
Corps Report on 2015 Columbia/Snake Warm Water, Fish Die-Off Will Discuss Actions to Avoid Repeat by Staff, Columbia Basin Bulletin, 4/1/16
Post-Mortem 2015 Snake River Sockeye Run; 90 Percent of Fish Dead Before Reaching Ice Harbor Dam by Staff, Columbia Basin Bulletin, 12/4/15
Report Analyzes Impacts, Causes of This Year's Warm Fish-Killing Water in Columbia/Snake by Staff, Columbia Basin Bulletin, 11/6/15
Snake River Sockeye: Lowest Return Since 2007, Captive Broodstock Program Increases Spawners by Staff, Columbia Basin Bulletin, 9/11/15
Smoke, Lower Air Temperatures Keep Lower Snake Cooler by Staff, Columbia Basin Bulletin, 8/28/15
Last Of Dworshak Water for August? 400 Snake River Sockeye Between Lower Granite, Sawtooth Basin by Staff, Columbia Basin Bulletin, 8/14/15
NOAA's Snake River Sockeye Salmon Recovery Plan:25 Years of Actions at $101 Million by Staff, Columbia Basin Bulletin, 6/12/15