The U.S. Army Corps of Engineers, Portland District says it will not perform a deep drawdown at the Willamette Valley’s Detroit Reservoir in the fall of 2025.
For 2025, USACE will operate Detroit Dam the same as previous years, which includes the fall reservoir drawdown and management for downstream temperature.
The National Marine Fisheries Service issued a Biological Opinion on Dec. 26, 2024 that included a fall deep drawdown at Detroit Reservoir to improve passage through the dam for fish species listed under the Endangered Species Act.
Because USACE has not analyzed the effects of a Detroit Reservoir deep drawdown, the agency says it plans to gather public input and complete a Supplemental Environmental Impact Statement in early 2026, which will result in a long-term decision for 2026 and beyond.
After NOAA had evaluated a revised proposed action for Willamette Valley dams submitted to the agency by the Corps in August 2024, it determined the proposed action would jeopardize the continued existence of upper Willamette River Chinook salmon and steelhead, both listed as threatened under the federal Endangered Species Act, and that the proposed action would result in adverse modification of the species’ designated critical habitat.
NOAA went on to list other salmonid species in the Willamette and Columbia river systems that would be adversely impacted, including Lower Columbia River Chinook salmon, Upper Columbia spring-run Chinook salmon, Snake River spring/summer-run Chinook salmon, Snake River fall run Chinook salmon, Columbia River chum salmon (O. keta), Lower Columbia River coho salmon (O. kisutch), Snake River sockeye salmon (O. nerka), Lower Columbia River steelhead, Middle Columbia River steelhead, Upper Columbia River steelhead, Snake River Basin steelhead, and Southern Resident killer whales (Orcinus orca) and their designated critical habitat.
“However, the proposed action is not likely to jeopardize the continued existence of these species or result in the destruction or adverse modification of their critical habitat,” NOAA concluded in its BiOp.
NOAA’s 2024 BiOp focuses on the Corps’ preferred alternative from the Corps’ Draft Programmatic Environmental Impact Statement for the Willamette Valley System, with some key additions and clarifications that focus on implementation, the BiOp says.
The BiOp says the proposed action consists of the continued operation and maintenance of the Willamette system for the congressionally designated authorized purposes of flood control, hydropower, irrigation, navigation, recreation, fish and wildlife, water supply and quality, as well as actions to ensure the system’s operations comply with the ESA.
“This includes the continued operation of existing structures and facilities, modifications to operations and construction, and operation and maintenance of new structures,” the BiOp says. “The new elements of the proposed action were developed to improve fish passage through the WVS dams using a combination of modified operations and new structures. It also includes measures to improve downstream water quality, balance water management flexibility, and reduce project effects for ESA-listed fish.”
In more detail, the BiOp lists as components of the proposed action as:
— An adaptive management and implementation plan, which is a roadmap that lays out the strategy and schedule for implementation, ongoing assessment of the proposed action, and proposed improvements to the Willamette Action Team for Ecosystem Restoration governance and coordination process.
— In addition, the BiOp action includes downstream fish passage structures to be constructed at Detroit Dam, Lookout Point Dam, and on a smaller scale at Foster Dam.
— A structure to improve downstream water temperature management to be constructed at Detroit Dam.
— Changes to operations to facilitate downstream fish passage at Cougar and Green Peter dams.
— The other operational change is a new integrated temperature and habitat flow regime.
Also see:
–CBB, Feb. 25, 2025, Corps Still Determining How To Implement Changes At Willamette Valley Dams With Funding Still Uncertain