FILE - Detroit Lake sits at a low water level during its typical winter drawdown, in Detroit, Ore., on Dec. 6, 2025. The U.S. Army Corps of Engineers plans to gradually lower Detroit Lake this month in an effort to help threatened Chinook salmon swim downstream.
Eli Imadali / OPB
The controversial drawdown of Detroit Lake is still on track for this fall.
A federal judge Wednesday rejected a request from multiple Marion County governments to block the U.S. Army Corps of Engineers from draining the reservoir’s water levels to historic lows. The county, and various cities downstream from the dam, say the move would damage their water systems — threatening local water supplies — and decimate certain fish species.
The Army Corps is lowering the reservoir to help threatened Chinook salmon move more easily downstream, which is required by a separate court order. Marion county and the cities of Salem and Stayton filed a federal lawsuit in July to prevent the drawdown.
In his written order, U.S. District Court Judge Mustafa Kasubhai said plaintiffs failed to prove that the drawdown was likely to cause irreparable damage. He said the local governments failed to provide enough evidence that harm would occur, saying there are significant differences between the Detroit Lake drawdown and previous drainage efforts at neighboring reservoirs.
Within hours, Marion County officials announced they would appeal the decision, asking for an emergency consideration from the 9th Circuit Court of Appeals.
“This new policy will devastate canyon communities, endanger drinking water for over 230,000 people living downstream, and even jeopardize the very fish it claims to be trying to save,” the county’s press release stated.
The Army Corps said in a press release on Thursday that it will start the drawdown later this month.
Related: Battle over drinking water, fish protections and Detroit Lake reaches federal court
The local concern stems from a previous drawdown at Green Peter Lake in 2023. In that case, the Army Corps lowered the lake at a rapid rate, turning up large amounts of sediment. The muddied water then disrupted water treatment plants in Lebanon and Sweet Home. The sudden drawdown also killed thousands of kokanee salmon, due to the sudden change in water depth.
The kokanee is a non-native species introduced into Detroit, Green Peter and other reservoirs in part to compensate sport fishermen for the decline in native salmon populations after the construction of dams throughout the Willamette River system.
Army Corps officials have said they plan to take a much more gradual approach in Detroit, incrementally lowering the reservoir over multiple years, reducing the amount of churned-up sediment.
Kasubhai wrote that he shared some of the local governments’ concern about the possibility that draining the reservoir could create high turbidity and make it more difficult to refill at a later time.
“But ‘possibility’ is not ‘likelihood,’ and the law requires parties seeking injunctive relief to demonstrate that the irreparable harm they fear is ‘likely’ to occur,” he wrote.
Colm Willis, chair of the Marion County Board of Commissioners, told OPB on Thursday that water systems located downstream from the time aren’t prepared for extreme levels of turbidity. And local officials don’t believe the Army Corps’ new strategy will prevent that damage.
“The reality of this situation is the Army Corps did this before in Green Peter,” Willis said “It’s just not true to say that we didn’t prove that similar damage was likely to happen in this case.”
The original lawsuit filed by local governments in Marion County will continue. The Army Corps said it will host more public information sessions to explain the drawdown. Locations and times will be announced within the week.
