April’s record rains and snowmelt sent torrents of water down the Willamette River’s tributaries and into its main stem.

With reservoirs full behind the basin’s dams, the U.S. Army Corps of Engineers opened the literal floodgates. As the water rushed downstream, fish that usually migrated upstream — spring chinook salmon and endangered winter steelhead — vanished. It wasn’t clear if they were unwilling or unable to navigate the high waters, if the floods had harmed the fish, or if the run had simply ended sooner than expected.

Wildlife officials held their breath as waters receded. Slowly, the fish came back. On Thursday morning, the Corps’ supervisory fisheries biologist, Greg Taylor, moved a truckload of wild winter steelhead over Fall Creek dam, a barrier the fish can’t pass without human help. He was happy to see the runs return.

These runs are closely monitored in the Willamette River basin and its tributaries. Fisheries scientists worry that precarious populations of winter steelhead could face local extinction in the coming years if things don’t change. Spring chinook populations are doing better but they’re still declining. A number of threats face salmon and steelhead in the Willamette, but the largest, by far, are the dams; there are 13 large dams on Willamette tributaries operated by the Army Corps of Engineers.

Along with other factors — like habitat degradation, overfishing, hatchery practices and poor ocean conditions — dams have caused populations of chinook salmon and steelhead to collapse, according to the Willamette River Biological Opinion. It was authored by the National Oceanic and Atmospheric Administration in 2008 and updated in 2015. The report detailed a number of steps the Corps should take to improve the river, steps which it is legally required to take under the Endangered Species Act. The Corps is quick to point out that some action has already been taken, though critics say they aren’t acting fast enough.

That sense of urgency, amplified by increasingly concerned Northwest conservation groups, led the advocacy group American Rivers to list the Willamette this week as one of the most endangered rivers in the country in 2019.

“There was an expectation that [the U.S. Army Corps of Engineers] would have made improvements to their dams within 10 years,” said Travis Williams, executive director of Willamette Riverkeeper, which first sued the Army Corps of Engineers over its dams in 2007. But some of the projects have been delayed.

Aerial view of Detroit Lake on Oregon's North Santiam River.

Aerial view of Detroit Lake on Oregon’s North Santiam River.

U.S. Army Corps of Engineers

Some of these dams are over 100 feet high and lack fish ladders to permit returning fish to continue upriver. The water impounded behind these insurmountable barriers doesn’t move or mix, so water at the top of the lakes becomes too warm for the fish, while water at the bottom becomes too cold. Depending on the time of year, that also means very cold or very warm water could be sent through the dams, making downstream temperatures inhospitable, too. Young fish returning downstream to the ocean either travel over the dams’ spillways or through the turbines. The pressure change can be deadly.

The Corps, advised by NOAA, can take on a number of projects proposed for the Willamette River Basin to save the fish. They include floating platforms and towers that can draw water from different depths in the reservoirs to help control water temperature downstream; collection sites that channel adult fish into holding pools, where they wait to be trucked up over dams and released again to spawn in the tributaries upstream; and downstream passages to help young move safely past the dams and out to sea.

Once they reach the ocean, the fish are vulnerable to threats from commercial fishing and challenging ocean conditions — some of which are the result of climate change. Unusually warm ocean waters may have caused fish populations to decline, and decreasing snowpack in the Cascades means that some of the fish’s spawning grounds are no longer productive.

But younger fish face the biggest challenges by far, and they’re the most difficult to overcome from an engineering standpoint.

“What we really stress in the biological opinion is that they need passage downstream,” said Anne Mullan, an endangered species biologist with NOAA. “There’s very low mortality for fish on the way up, but there’s just not safe passage downstream.”

About 2,400 winter steelhead had been counted going above Oregon City’s Willamette Falls as of April 2, 26 miles upriver from the Willamette’s mouth. According to NOAA, between 3,000 and 4,000 steelhead could swim up the Willamette before the year is over. That’s more than double last year’s run and significantly higher than the all-time low of 800 fish counted in 2017.

But that isn’t cause to celebrate, Mullan said.

“If we hit 4,000, it might be the fifth-lowest run. Maybe the sixth,” she said. “It’s an uptick compared to the last two years, but it’s not even going to reach the 10-year average.”

And that 10-year average that has also been declining.

The Oregon Department of Fish and Wildlife considers steelhead populations to be imperiled enough that in 2018 it took the drastic step of killing sea lions that predated on the fish at Willamette Falls.

Plans for a downstream passage for fish at Cougar Dam on the McKenzie River were delayed, and now the construction isn’t expected to be completed until 2022.

The Corps is quick to point out that some of the projects on NOAA’s list have been completed. They installed a temperature-control tower at Cougar Dam on the South Fork McKenzie River east of Springfield and made improvements to the adult fish collection facility east of Salem on the Santiam River, where fish are transported upstream and over the dams. They’ve also changed the ways they release water to try to improve downstream temperatures until they can build more temperature-control towers. Other projects, though, have stagnated.

Modifying dams is expensive and challenging, the Corps says — far more difficult than simply building a fish ladder.

“These things take time, and it’s important to do them right,” the Corps’ Greg Taylor said. “If we do them too fast, they’re not right, that’s bad. And if we take too long, the populations go extinct.”

In some cases, modifying the dams has proved controversial. The U.S. Army Corps of Engineers has been sued twice recently over proposed fish-friendly modifications to dams on the Santiam River, a tributary of the Willamette — by environmental groups who think they’re not acting fast enough and by people who live and recreate on the Santiam that think the project shouldn’t happen at all because it might endanger their water supply.

The pace is frustrating to the environmental groups that have been advocating for fish-friendly dam modifications for more than a decade. “It just feels like the Willamette isn’t a priority,” Williams said.

Taylor said the Corps is working with NOAA to re-evaluate their plans for dam improvements. He said some timelines might get moved up, but others might get delayed.

That’s not acceptable to Williams. “We don’t want to see timeline extensions. We want to see work on these projects,” he said.

It’s hard to tell if any of the changes the Corps and Oregon Department of Fish and Wildlife have made are helping the fish, said Anne Mullan of NOAA. The populations are so vulnerable to things like climate change and ocean temperatures. A combination of El Niño and a warm water phenomenon called “the blob” could have played a role in the low runs of 2017 and 2018, masking any benefit from the dam improvements.

But scientists do know that restoring passage for fish to good habitat works. And while populations are extremely low, Mullan said, things aren’t dire yet. “There’s a kind of resilience there, even if we get below a thousand fish. If we can get them up to spawning ground, we can see a return,” she said.

Anne pointed to extreme examples, like areas where dams were entirely removed and populations rebounded. That’s not an option for any of the Willamette’s dams. They provide crucial flood control in the rainy spring, help irrigate farms during dry summers and provide hydropower. While modifying them is challenging and expensive, Mullan said it’s worth it.

“These things take a long time to get done,” Mullan said, “but they are, in our opinion, the strongest improvements needed. We need passage upstream and passage downstream.”