PORTLAND, Ore. -- The U.S. Army Corps of Engineers is modifying operations at Detroit Dam to improve juvenile salmon downstream passage survival by releasing water exclusively through the upper regulating outlets when downstream passage rates are high.
Normally, the Corps allows water to flow through turbines for power generation. Instead, the Corps will not operate the turbines between the hours of 6-10 a.m. and 6-10 p.m., except in the case of emergencies, from Nov. 1, 2020 – Feb. 1, 2021. Research shows that juvenile salmon downstream passage rates are high during these times.
The operation is part of a suite of interim measures that the Corps is planning to implement to benefit Endangered Species Act-listed salmon in the Willamette River Basin while it works to complete the Willamette Valley System Environmental Impact Statement and associated Endangered Species Act consultation on the Corps’ operation and maintenance of the Willamette Valley Project.
“Through collaboration between experts from the Corps and the National Marine Fisheries Service, we were able to identify actions to benefit salmon that can be implemented during the interim period until the ongoing environmental reviews are complete,” said Erik Petersen, Willamette Valley operations project manager. “This operation will improve the survival rates of juvenile salmon during periods of high downstream fish passage while avoiding impacts to our flood risk management mission and the City of Salem’s water supply.”
Corps biologists will install and operate a rotary screwtrap below Big Cliff to provide information on the migration timing and size of naturally produced juvenile salmonids exiting downstream of Detroit and Big Cliff. They will then compare results to rotary screwtrap results previously collected under normal operating conditions to determine the effectiveness of the operational change.
The Corps will also manage discharge from Detroit Dam to minimize total dissolved gas levels downstream of Big Cliff Dam. In addition, this operation does not impact flood risk management operations.
Corps managers also adjust operations, when water levels make it possible, by releasing water through Detroit Dam’s spillways during summer months to make downstream water temperatures and habitat better for salmon survival.
Willamette Valley Project: The U.S. Army Corps of Engineers operates 13 dam and reservoir projects in the Willamette River drainage system. Each dam contributes to a water resource management system that provides flood damage reduction, power generation, irrigation, water quality improvement, fish and wildlife habitat and recreation on the Willamette River and many of its tributaries. Since their completion, the dams have cumulatively prevented over $25 billion in flood damages to the Willamette Valley. For more information, visit: www.nwp.usace.army.mil/.