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Howard Prairie Reservoir in Jackson County near Ashland, Oregon, in June 2021.

Numerous locations in the Northwest broke all-time records for high temperatures between June 26 and June 30, causing climatologists to warn of worsening drought and a shrinking water supply from added demands.

In the Columbia Basin—where the heat wave continues—fish managers and hydroelectric dam operators are working to prevent a repeat of 2015, when an estimated 250,000 adult sockeye salmon perished in the warm waters of the Columbia River.

Preventive measures being taken include releases of cooler water from the Clearwater River at Dworshak Dam; trapping and hauling of adult salmon at Lower Granite Dam on the Snake River; flow augmentation in the upper Snake, Payette and Boise systems; and close monitoring of water temperatures and fish passage counts at lower Snake and Columbia river dams to see if sockeye or Chinook are holding back due to warm water.

The Oregon Department of Fish and Wildlife also implemented emergency regulations on July 1, and closed fishing for salmon, steelhead, sturgeon and trout from 2 p.m. until one hour before sunrise in several other rivers and streams to help them survive.

"We generally don't experience this sort of heat," Oregon State Climatologist Larry O'Neill said at a June 28 drought webinar hosted by the National Oceanic and Atmospheric Administration's National Integrated Drought Information System.

O'Neill said the heat wave itself is "unprecedented," and while the high-pressure pattern is similar to that of other Pacific Northwest heat waves, "the high-pressure center is much more intense than it has been in the historical data record.”

Portland exceeded all-time high-temperature records for three consecutive days, hitting 108 degrees Fahrenheit on June 26, 112 on June 27, and 116 on June 28, according to a July 1 update by NIDIS.

Seattle-Tacoma International Airport had a two-day record-breaking streak of 104 on June 27 followed by 108 on June 28.

The highest recorded temperature in the two states was 118 on June 28 at The Dalles, Washington, and Hermiston, Oregon.

According to NOAA's Northwest River Forecast Center, the average temperature departure from normal for June 1 through June 30 was more than 6 degrees almost everywhere in the Columbia Basin and western Washington and Oregon, except for far coastal areas and two basins in British Columbia, which were between 1 and 6 degrees above average.

"This week, high temperatures ranged from 20 to 30 degrees above normal, breaking multiple records," the U.S. Drought Monitor reported on July 1.

Before the heat wave hit, the region was already suffering from significant drought. O'Neill said Washington, Oregon and Idaho experienced their second-driest spring—March, April and May—since 1895. Many rivers were already recording below-average streamflows, especially in central Idaho and much of western Oregon and Washington. Nineteen counties in Oregon and at least 10 counties in Idaho have declared drought emergencies, and a lack of rain has left extremely dry soil conditions.

"It's definitely going to worsen drought conditions across the Northwest," Troy Lindquist, senior hydrologist for the National Weather Service in Boise, said at the June 28 webinar. He noted that many reservoirs are underfilled, and heavy irrigation demand is drawing down some reservoirs earlier than usual. Hydrologists are expecting well-below carry-over going into the next water year, he said.

Low river flows and high air temperatures also lead to significant increases in river temperatures, impacting salmon survival and migration. Salmon and steelhead begin to experience difficulties and sometimes stall their migration when river temperatures reach 68 F.

"We've avoided high-temperature impacts until now," U.S. Army Corps of Engineers representative Chris Peery said at a June 30 Columbia River Technical Management Team meeting. However, he noted, as water temperatures continue to rise, sockeye salmon, summer Chinook and other migrating adults could face challenges.

The team discussed multiple efforts to help salmon and steelhead as they migrate through increasingly warm water in the Snake and Columbia rivers. Sockeye salmon are just beginning their journey, with the majority migrating up the Columbia River to lakes in the Okanogan and Wenatchee river watersheds, and to B.C.

Only the Snake River sockeye heading to Stanley Basin lakes are listed as endangered under the Endangered Species Act. To help them complete the journey, the Idaho Department of Fish and Game implemented an emergency trap-and-haul plan to prevent the kinds of losses seen six years ago, when an estimated 95 percent of Snake River sockeye died in the river between Bonneville and Lower Granite dams. "The frequency of these events is expected to increase, with an 80 percent decline in adult migratory survival projected to occur by the 2040s under current climate projection scenarios," the plan states.

Jonathan Ebel, who represents Idaho on the TMT, said crews from NOAA Fisheries and Idaho plan to trap sockeye at Lower Granite Dam from July 6 through July 23, enabling them to transport half of the adult sockeye from the uppermost Snake River federal dam to spawning locations. The contingency plan says that transporting sockeye to higher elevations is a valuable tool under emergency situations, but involves a tradeoff with the long-term goal of restoring a healthy, self-sustaining population that can migrate from the ocean to spawning grounds.

Ebel said his agency does not plan to trap sockeye at Ice Harbor Dam—the first they encounter on the Snake River. The plan notes that a significant portion of sockeye trapped at the Snake River's lowest dam are strays from the Columbia River.

"Our strategy is to do everything necessary to get them to Granite," Ebel told fellow TMT members. He said they are more prepared than they were in 2015, and this year, they are starting the trap-and-haul program significantly earlier. Idaho and NOAA crews will adapt plans as necessary, he added.

"We'll get through this, and if we need help, we'll let other entities in the basin know," Ebel said.

Claire McGrath, representing NOAA Fisheries on the TMT, said that sockeye began migrating later this year compared with other years, but adult passage at the dams has picked up. As of June 30, about 95,400 sockeye were counted passing Bonneville Dam, with 124 of them reaching Ice Harbor, the lowermost Snake River dam, and just 12 continuing past Lower Granite Dam.

McGrath said river flows in the Columbia River are higher than they were in 2015, but the extended heat wave will likely push the Columbia's water temperatures to levels reached in 2015.

"We'll just hope anything we can do for temperature management will keep those fish moving through the Columbia River and lower Snake River," she said.

Water temperatures in the Snake River—where flows are considerably lower than the Columbia River's—are already a concern, prompting the Corps to begin flow augmentation from Dworshak Dam earlier than normal.

Corps representative Jon Roberts told TMT members that in Lewiston, Idaho, at the confluence of the Snake and Columbia rivers, forecasters expected some relief by July 1, but temperatures were still expected to exceed 100 F, and only begin to dissipate on July 6. Snake River temperature gauges at Anatone, Washington, and Orofino, Idaho, were already at 74. "We'll see those continue to climb with at least another two days of intense heat," he said.

Roberts said he expects to see the surface water in the forebay reach 80 as the heat wave continues. But, he said, he's focused on temperatures from 15 to 20 meters below the surface, where pumps pull water to cool the fish ladders and encourage salmon to continue the journey. "It's important to keep that in the cooler range, so the ladder differential doesn't get too far."

The Corps plans to continue spilling water at Dworshak through July 9, and attempt to maintain the tailwater temperature at Lower Granite Dam at 68, Roberts said. "We'll continue to evaluate that every day, and make a reduction as soon as we can" to save the cooler water for later in the summer, he added.

A June 30 water supply forecast by the Northwest River Forecast Center shows the Snake River is predicted to have 34 percent of its average April-through-August water supply at American Falls Dam, and 57 percent at Lower Granite Dam. The Columbia River is faring better, but is still significantly below normal, with the forecast predicting 64 percent of normal supply at Grand Coulee Dam and 63 percent at The Dalles Dam.

Even when the heat wave eases, forecasters say above-average temperatures and below-average precipitation are predicted to continue through the summer.

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K.C. Mehaffey covers fish issues for Clearing Up, and is editor of the NW Fishletter. She joined the NewsData writing team in February 2018. From lawsuits to scientific studies, she is enjoying the deep dive into the Columbia Basin's many fish topics.