Deep drawdowns planned at two Willamette Valley Project reservoirs are bringing a greater sense of urgency from Bonneville Power Administration and the Public Power Council for completing studies needed to deauthorize the system's hydroelectric projects.
The U.S. Army Corps of Engineers announced earlier this month it will begin gradual drawdowns at reservoirs behind Lookout Point and Green Peter dams in June, and bring them to historically low levels to aid juvenile fish passage.
The dams are among 13 operated in the Willamette River basin by the Corps as the Willamette Valley Project, eight of which produce power. Lookout Point and Green Peter dams together have total capacity of about 200 MW, about half of the project's total capacity of 408 MW. They are two of the three highest-capacity federal projects on the Willamette, along with Detroit Dam, which has a total capacity of 100 MW.
"We are very concerned to be learning about deep drawdowns at these two Willamette projects, which only further reduces the already limited power output from the overall Willamette systems," Scott Simms, CEO and executive director of the Public Power Council, told Clearing Up. "These negative power production impacts are one more reason why we absolutely must get Willamette project power purposes and cost allocations reexamined by Congress, so the projects can be fully devoted to their other purposes and completely supported financially by U.S. taxpayers, not Northwest ratepayers," he added.
The deep drawdowns are part of an interim injunction for operating the dams following a September 2021 final order by Oregon U.S. District Judge Marco Hernandez in Northwest Environmental Defense Center et al. v. U.S. Army Corps of Engineers et al. [18-437] (Clearing Up No. 2021). The drawdowns are designed to increase juvenile spring Chinook and steelhead survival through the reservoirs and past the dams.
In an email to Clearing Up, BPA spokesman Kevin Wingert said the hydroelectric dams in the Willamette Valley Project are already among the highest-cost dams in the Federal Columbia River Power System. He said unlike the Snake and Columbia river dams, they are not operated to support integration of new clean-energy resources, and are not able to support resource adequacy during times of high system demands. "The big picture is that these operational impacts from the injunction measures, combined with the high costs for fish passage structures, lead Bonneville to estimate that commercial power from the Willamette dams is uneconomical."
BPA Administrator and CEO John Hairston reiterated that concern in a statement to a subcommittee of the U.S. House Committee on Natural Resources on May 23. "The 2022 Water Resources Development Act directed the Corps to conduct disposition studies for power purposes at eight Willamette dams. Bonneville estimates that power production from Willamette Valley systems will be even more uneconomical with diminished operations and additional structural costs proposed by the U.S. Army Corps of Engineers. Bonneville is eager to complete the disposition studies for consideration by Congress," he told the committee. A report is due to Congress by June 2024.
According to a Corps May 10 news release, Lookout Point's reservoir will be drawn down to 750 feet, which is about 80 feet lower than it's been since the dam's construction. Under the injunction measures, the average annual generation at Lookout Point is estimated to decrease by about 58 percent, Corps spokesperson Kerry Solan told Clearing Up via email. That includes a reduction of about 30 percent during the winter peak period, a decrease of about 60 percent during the spring off-peak period and a decrease of about 68 percent during the summer peak period, she said.
Green Peter's reservoir will be drawn down to a surface elevation of 780 feet, which is about 120 feet lower than it's been since the dam was built. Average annual generation at Green Peter Dam is estimated to decrease by about 33 percent, Solan said. That includes a decrease of about 40 percent during the winter peak period, an increase of about 10 percent during the spring off-peak period and an increase of about 30 percent during the summer peak period, she said.
Both dams will reach these low elevations in November and be kept there for about a month. The reservoirs will begin refilling according to a rule curve—used to determine needed flood storage—in mid-December. They will be held just above the spillway crest until the following summer's drawdown operations.
"It's important to note that while this is the current 2023 plan, operations may be refined in future years as the Corps learns more about fish passage and survival, and the benefits from drawdown operations," Kathryn Tackley, a physical scientist for the Corps, said in the news release.
Simms noted PPC has been working for several years to get the power purposes removed from certain Willamette projects, and said both Democrats and Republicans in Congress have supported their efforts.
"Congress heard our concern and supported it with a very clear directive to the Corps to complete a power deauthorization study in 18 months, so now we must ensure the Corps can deliver that study to Congress so they can take action," he said. "We had the Corps' [Northwestern] Division [commanding] general Geoffrey Van Epps as a guest at our PPC Executive Committee meeting last month and discussed our expectations to conduct this study in a comprehensive manner and to deliver it to Congress on time. As well, we made it clear that they have our commitment to help in any way we can—we at PPC want to be a partner as they work to fulfill this important mandate from Congress," Simms said.
Wingert noted that drawdowns are also occurring at the Cougar Dam reservoir, which has a total capacity of 100 MW.
"It is also important to remember that these operations under the injunction are recommended by an expert panel that through the adaptive management process can and has recommended longer periods of drawdown operations to pass fish, and use of spill when reservoirs are not drawn down. These operations extend across the timing of juvenile migration, but they can also leave reservoirs depleted for longer periods of the year, depending on rainfall," he said.
BPA is working with the Corps to complete the studies to determine if there is remaining federal interest in commercial power production from the Willamette dams and to confirm that deauthorization of power will not affect other purposes, such as flood risk management.
Wingert noted that power generation from the Willamette Valley Project comes after all other authorizations and obligations for the Corps have been met, so generation from these projects is already constrained. "That said, while the [Willamette dams] may not directly be operated for the purposes of renewable integration or resource adequacy, BPA uses any available generation from the [dams] to holistically support the mission and priorities of BPA," he said.
In addition to implementing measures in the injunction and conducting a study to evaluate deauthorizing power as a purpose at the Willamette dams, the Corps is completing an environmental impact statement to guide management of the dams and reservoirs for the next 30 years. In its draft EIS, the Corps found that near-term operations due to court-ordered mitigations will decrease power generation by 52 aMW, from the current 171 aMW, resulting in power generation that is no longer economically viable (Clearing Up No. 2084).
