Idaho will begin a trap and haul operation at Lower Granite Dam July 6 to rescue endangered Snake River sockeye salmon, an operation they first did during the heat-caused sockeye die off in 2015.

Although few sockeye have arrived in the Snake River, water temperatures in the river are rising due to an extended heat wave that has seen multiple days with temperatures above 100 degrees Fahrenheit, and they are especially rising in tributaries, such as where the Salmon and Snake rivers meet. Those expected temperatures at Lower Granite Dam are driving Idaho’s preparedness for the trap and haul operation.

Despite releases of cold water from Dworshak Dam, tailwater temperatures at Lower Granite Dam, where the trap and haul operation will take place, have risen from 65 degrees F a week ago to 67 to 68 degrees F. Wednesday, June 30.

“There’s at least another two days of high heat in our region and the temperatures will plateau, but still at high temperatures,” Jonathan Roberts of the U.S. Army Corps of Engineers warned the interagency Technical Management Team at its meeting Wednesday, June 30. In addition, high water temperatures upstream of Lower Granite at the Corps’ Anatone gauge will likely reach the Snake River dam in the next couple of days, he said.

See NOAA’s 10-day weather outlook for the Northwest region.

To keep the tailwater temperature at Lower Granite Dam below the 68 degree F. temperature called for in the 2020 Federal Columbia River Power System biological opinion for salmon and steelhead, the Corps has been passing Dworshak Dam’s water at a rate of 12,500 cubic feet per second through a combination of spilling over the dam and passing water through the powerhouse. The Dworshak water, Roberts said, could last through mid-August.

Still, tailwater temperature at Lower Granite will likely rise and hit a high of near 69 degrees for several days as the heatwave plays itself out, so “we will need to continue the discharge from Dworshak after that to get the temperature back down.”

One additional option with Dworshak, Roberts said, is to spill about 500 cfs more water at night, but it would show little to no improvement in water temperature at Lower Granite and it would shorten the time of using Dworshak water by one day.

Also to cool Lower Granite’s tailwater, the Corps is considering closing the dams Removable Spillway Weir as soon as possible. It had issued an announcement to river and fisheries managers June 29 saying that it would close the RSW July 1 or 2. The change would lower the tailwater temperature by about 1 degree F, Roberts said, but if the closure extended for more than 48 hours, it could also result in a rise of the dam’s forebay temperature at the 1 to 5 meter mark and lower.

“Closing the RSW now could also raise the temperature at the 15 meter level, which is where the water is pumped for the fish ladder and the trap,” he said. “Closing the RSW now likely won’t improve the situation as we had hoped.”

A normal spillgate opens from 50 to 60 feet below the river surface, forcing migrating juvenile fish to sound deeply to find the opening. The RSWs are inserted in an open gate, effectively blocking the lower end of the opening and bringing the flow nearer the surface.

Another issue is Lower Granite’s forebay temperature.

“At the end of the day when it is hottest (speaking of the current 100 plus degree days) the forebay surface temperature can reach as high as 80 degrees,” Roberts said.

However, water in the forebay at the 15 meter level was about 67.2 degrees June 30 at 10 am and at the 20 meter level it was at 65.2 degrees F (see http://pweb.crohms.org/ftppub/water_quality/tempstrings/LWG_S1_2021_06.html). This stratification, he said, is important because water from lower water levels in the dam’s pool is drawn through pumps to cool the fish ladder and the fish trap where sockeye will soon be trapped and hauled.

Migrating adult sockeye hit a thermal block in 2015 as river temperatures rose considerably above the 68 degree F limit. Some 90 percent of sockeye died before reaching Ice Harbor Dam, the lower of the four Snake River dams. IDFG, NOAA Fisheries and the Nez Perce Tribe set up a rescue project at Lower Granite Dam to trap the adults and haul them to the hatchery at Eagle, Idaho, which Jonathan Ebel of Idaho Fish and Game said they are ready to do again this year.

See CBB, December 4, 2015, “Post-Mortem 2015 Snake River Sockeye Run; 90 Percent Of Fish Dead Before Reaching Ice Harbor,”

Ebel said that the agency would trap and haul sockeye at Lower Granite Dam July 6 through July 23, “unless we see a change in sockeye passage.” The change would be a continued inability of the fish to pass through Snake River dams and in that case the fisheries agency could continue to trap and haul past July 23.

IDFG’s 2017 trap and haul emergency procedures are here.

When IDFG begins the trap and haul operation on July 6, historically about 10 percent of the sockeye would already have passed Lower Granite Dam. “We hope we will hit the peak of the run during the operation,” Ebel said.

The state agency will trap the fish four days a week – Monday through Thursday – he said. On those days, it would trap about 70 percent of the fish that would have passed the dam and overall through a full week, it would trap and haul about 50 percent of the total run. IDFG will not consider trapping at Ice Harbor Dam this year, he said.

“The difference between this year and 2015 is that we were not as prepared in 2015,” Ebel said. “This year all of our transport staff is lined up and we’re starting earlier than in 2015.”

Some 8,000 to 10,000 sockeye have passed Bonneville Dam over the past few days. The total at the dam as of June 29 was 87,882 fish, 49.8 percent of the count on the same day last year (176,559), and 46 percent of the 10-year average (187,685), according to NOAA Fisheries’ Clair McGrath at TMT.

Of those, 420 have been Snake River sockeye, she said. That’s based on an extrapolation of PIT-tags detected at the dam.

“It appears that travel time through the lower Columbia River are slower this year,” McGrath said. “They are arriving in the Snake River about one week late.

Sockeye returns this year are predicted by the U.S. v Oregon Technical Advisory Committee at a low 155,600 fish at Bonneville Dam, with just 700 of those heading into the Snake River where the sockeye were listed as endangered under the federal Endangered Species Act in 1991. Some 100 will turn into Oregon’s Deschutes River and the remainder will head up into the mid-Columbia River. The forecast is more than half the actual run in 2020, which was 345,018 fish.

The farther upstream, the lower the counts are at dams. The count of sockeye at McNary Dam is 43,489, also on June 29, which is 49 percent of last year’s count of 87,625 and 46 percent of the 10-year average of 93,465.

Some 76 sockeye have reached Ice Harbor Dam (last year 52 and the 10-year average is 115), the lowest of the four lower Snake River dams, and just 9 have passed Lower Granite Dam (last year 6 and the 10-year average is 15), the upstream of the four dams.

Snake River sockeye face a long and arduous journey, traveling about 900 miles and 6,000 vertical feet to return to their spawning sites in the Sawtooth Basin.

A 2020 NOAA Fisheries study said that the 2015 die off of sockeye in the Snake River may represent a “new normal” with climate change. The scientists predicted “catastrophic consequences for the endangered species.”

The warmer regime will likely reduce the survival of highly endangered Snake River sockeye salmon by about 80 percent from its already low levels. In recent years, only a few hundred Snake River sockeye have survived their annual upstream journey from the ocean to the mountain lakes where they spawn in Central Idaho. In 2020, just 639 sockeye migrated past Lower Granite Dam, but they still were faced with migrating hundreds of miles to the Central Idaho lakes.

Sockeye salmon are especially vulnerable to temperature changes because they migrate upstream during the hottest part of the summer. Survival of the fish is likely to fall sharply as temperatures rise in the coming decades, according to the NOAA study.

Mid-Columbia River sockeye are also arriving in tributaries upstream of dams, but the water temperature is rising there as well, said Charles Morrill of the Washington Department of Fish and Wildlife. “We need to worry about a repeat of 2015,” he said.

One difference this year is that river flow levels are a little higher, McGrath said.

More than 6,000 of the fish have passed Priest Rapids Dam, the lowest of the mid-Columbia dams. That’s 41 percent of last year’s passage on June 29 of 14,852 fish, and 22 percent of the 10-year average of 27,116 sockeye.

For background, see:

— CBB, June 24, 2021, “Intense Heat Wave Prompts Earlier Dworshak Water Releases To Cool Lower Snake River AS ESA-Listed Sockeye Soon To Arrive,” https://columbiabasinbulletin.org/intense-heat-wave-prompts-earlier-dworshak-water-releases-to-cool-lower-snake-river-as-esa-listed-sockeye-soon-to-arrive/

— CBB, January 8, 2021, “Another Low Upriver Spring Chinook Run Forecasted For 2021, Snake River Sockeye Projected At Only 700 Fish; Better News Downstream Bonneville Dam,” https://columbiabasinbulletin.org/another-low-upriver-spring-chinook-run-forecasted-for-2021-snake-river-sockeye-projected-at-only-700-fish-better-news-downstream-bonneville-dam/

— CBB, August 27, 2020, “Snake River Sockeye Nears End Of Run At 68 Percent Of Average, Fall Chinook Passage Gaining Steam; Cool Down In Lower Snake,” https://columbiabasinbulletin.org/snake-river-sockeye-nears-end-of-run-at-68-percent-of-average-fall-chinook-passage-gaining-steam-cool-down-in-lower-snake/

— CBB, October 15, 2020, “NOAA Fisheries Study Warns Climate Change Poses ‘Catastrophic’ Threat To Survival Of Endangered Snake River Sockeye,” https://columbiabasinbulletin.org/noaa-fisheries-study-warns-climate-change-poses-catastrophic-threat-to-survival-of-endangered-snake-river-sockeye/

— Mike O’Bryant, [email protected]