Dam operations are significantly impairing the survival of threatened fish species in the Willamette River Valley, according to a study by the National Marine Fisheries Service (NOAA Fisheries). The biological opinion, released on Dec. 26, 2024, found that Willamette Steelhead and Chinook salmon remain threatened across the Willamette River Valley.
A biological opinion is a document meant to determine whether federal actions like dam operations are likely to endanger the existence of a protected species or adversely affect a critical habitat. These documents also provide a reasonable and prudent alternative (RPA) if operations are found to jeopardize these species and habitats. To increase the odds of fish survival over time, the NOAA Fisheries is expediting studies and recommending structural improvements to Willamette River Valley dams.
Jennifer Fairbrother of the Native Fish Society, a nonprofit dedicated to the conservation and protection of wild fish, says drastically lowering water levels is essential to ensure the survival of threatened fish. “When you draw down those reservoirs and they turn back into river channels, you don’t have to contend with a lot of those other issues that the fish deal with when the reservoirs are full,” Fairbrother says.
The biological opinion came almost four years after a federal judge ordered the U.S. Army Corps of Engineers to conduct deep drawdowns in Willamette Valley reservoirs to improve juvenile fish passage and protect crucial spawning habitats that increase salmon populations.
Environmental advocates hope that drawdowns, structural improvements and decreased hydropower operations will help save these threatened fish from extinction in the Willamette River Valley. A drawdown significantly lowers water levels in reservoirs to allow easier passage of juvenile native fish through dam infrastructure.
In most cases, when reservoir levels are high, there are only two viable options for young fish to pass through dams without human assistance — over the spillway or through the turbines. Neither is ideal: Reservoirs are not typically full enough to allow for fish to swim over the top of a dam and fish mortality through power turbines is high. Several Willamette Valley dams have structures that are intended to allow for fish passage, but many of them require human intervention.
There is a third means of passage through holes known as regulating outlets, in the dam located deep under the water line that do not serve a hydroelectric purpose. Juvenile fish are unable to pass through these outlets during high water levels due to pressure and an inability to dive and locate them.
While some are authorized by Congress for hydropower, recreation and water supply, the primary function of Willamette Valley reservoirs is flood control — not to generate power or provide drinking water. “You actually maximize that flood control purpose when the reservoirs are lower,” Fairbrother says.
The biological opinion addresses 13 dams within the Willamette River Valley, home to the Willamette River, the McKenzie River, the Santiam River and Fall Creek, a major tributary of the Willamette River. Deep drawdowns will affect three major dams: Green Peter Dam on the Middle Santiam River, Lookout Point Dam on the Middle Fork Willamette River and Fall Creek Dam. Moderate drawdowns will affect Hills Creek Dam on the Middle Fork Willamette River, Foster Dam on the South Santiam River and Cougar Dam on the South Fork McKenzie River.
Along with drawdowns, several structural improvements will be made to Willamette dams. They include two methods: volitional and non-volitional fish passage. Volitional means fish can pass through a dam unassisted by human intervention, and non-volitional means fish require human assistance to pass. At Lookout Point Dam, a new juvenile downstream passage structure called a “floating surface collector” is projected to be operational by 2038. This structure will trap fish to be hauled by trucks downstream.
At Cougar Dam, an “extended chute” will be built by 2030 intended to ease the passage of juvenile fish through the earlier mentioned deep holes in the dam. Cougar Dam will also see a modification made to an existing water diversion tunnel, allowing fish to pass through without mortality. This tunnel will be operational during both drawdowns and normal water levels. However, it is expected to be used more during drawdowns when fish are more likely to encounter it. This modification is contingent on congressional authorization, which the Army Corps expects by around 2033.
At Green Peter Dam, a new upstream adult facility is to be constructed at the base of the dam by 2030. This facility will be designed to trap adult fish returning to their spawning grounds at the base of the dam and haul them upstream to continue their journey. Several other dams in the Willamette Valley will see similar structural improvements along with the scheduled drawdowns.
Fairbrother says the Native Fish Society and other environmental groups advocate for deep drawdowns over trap-and-haul passage methods because fish just don’t like interacting with human technology. “It’s just kind of a cascade of trying to get a wild animal to work within this technological solution. It just has not been shown to be effective,” Fairbrother says.
The Detroit Reservoir and dam on the North Santiam River was also scheduled to conduct drawdowns in fall of 2025. However, a press release from the Army Corps states that drawdowns at the Detroit Reservoir will not occur until the Corps can gather public input and complete a supplemental environmental impact statement. The Army Corps projects this impact statement to be completed by early 2026. Once it is completed, a decision will be made whether or not to conduct drawdowns in the reservoir. The delay is largely due to concerns over water quality as Salem and Stayton both use water downstream of Detroit Dam as drinking water.
Drawdowns may increase the amount of suspended sediment moving downstream known as turbidity, which can harm water quality. During the 2024 deep drawdown of Green Peter Reservoir, increased turbidity put significant stress on water treatment facilities in Lebanon, Sweet Home and Albany. This resulted in the Army Corps halting the drawdown ahead of schedule.
Fairbrother says this increase in turbidity is likely temporary and will subside as the rivers re-establish their channels. “I do expect us to see increased turbidity from drawdowns, you know, in the coming years from baseline levels. But again, I’m hopeful that those will continue to decrease in this level of severity,” Fairbrother says.
According to a scenario modeled by the Army Corps, Willamette Valley dams may no longer be able to adequately generate hydropower during drawdowns. Annual hydropower generation in the Army Corps’ Willamette Valley System could decrease from an average of 171 megawatts (aMW) to 93 aMW, which is a 45.6 percent reduction in power produced by the Willamette Valley System.
Advocates say that despite this, operating costs of the Willamette River Valley hydropower projects far exceed revenue generated. “This is a place where hydropower does not make sense and is outrageously expensive,” says Kathleen George, a tribal councilwoman from the Confederated Tribes of the Grand Ronde.
A 2022 Environmental Impact Statement by the Army Corps projects that hydropower at Willamette River Valley dams will operate at a net loss of anywhere between $639 to $939 million over the next 30 years. “If drawdowns are a viable solution, why don’t we invest in those and not go down this road of spending billions of dollars on something that we’re really uncertain is going to actually be able to do what we need it to do,” Fairbrother says.
In an email to Eugene Weekly, the Army Corps of Engineers wrote that hydropower projects have some environmental benefits — even if it’s hard for fish to pass through the turbines. Jeffery Henon, deputy chief of the Army Corps of Engineers public affairs office, writes, “Hydropower generation reduces the amount of total dissolved gas (TDG) downstream of the dams.”
TDG is the concentration of gasses like oxygen, nitrogen and carbon dioxide that dissolve in water. High concentrations of TDG is harmful to fish, causing gas bubble disease, where excess amounts of gas bubbles form in their bodies, and can cause injury and death.
In addition to the recently released biological opinion, former President Joe Biden signed the Water Resources Development Act (WRDA) of 2024 into law on Jan. 4. The act covers a wide range of hydropower projects, and mandates the Army Corps to evaluate an alternative that ceases hydropower production in the Willamette River Valley.
As salmon populations continue to decline, advocates say they are hopeful that the NOAA and the Army Corps of Engineers will act in a way that increases the ability for threatened species to survive in the Willamette River Valley. Advocates hope the Corps will ultimately cease hydropower operations and continue with drawdowns to secure a future for the threatened salmon. “We now, for a short period of time, still have the choice to save Willamette salmon,” George says.
