Marion County Announces Appeal After Judge Declines to Block Detroit Lake Drawdown

Marion County, OR. — Marion County announced Nov. 4 that it would appeal a federal judge’s refusal to temporarily block the U.S. Army Corps of Engineers’ planned fall drawdown of Detroit Lake, escalating a dispute over drinking water, fish protection and downstream impacts.

U.S. District Judge Mustafa T. Kasubhai denied the county’s request for a preliminary injunction, according to the county’s announcement. The county said it would seek an emergency injunction from the U.S. Court of Appeals for the Ninth Circuit while pursuing its appeal.

“We are extremely disappointed in today’s decision, but this fight is far from over,” said Marion County Commission Chair Colm Willis.

The denial leaves the drawdown unblocked by the requested injunction. It does not resolve the underlying lawsuit, which remains pending in District Court, according to the county.

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Marion County filed the lawsuit May 13, seeking to pause the drawdown until the Corps completes a report examining turbidity problems associated with operations at nearby Green Peter Lake and provides an opportunity for informed public comment. The county alleges the agency missed a deadline imposed by federal law.

County officials warn that deeper drawdowns could disturb reservoir sediment, increase downstream water-treatment challenges and threaten water supplies serving more than 220,000 people. They also cite potential consequences for agriculture, recreation and canyon communities dependent on tourism.

The Corps has offered a different assessment of the immediate risks. In a July 28 explanation of its plans, the agency said the 2026 operation would lower Detroit Reservoir to an elevation of 1,425 feet, a level previously reached in 2015 and 2019 without reported drinking-water impacts. The agency said it did not expect this year’s operation to affect drinking water.

The Corps describes the drawdown as a measure to improve passage for juvenile fish and protect endangered species. Its plan calls for progressively deeper fall operations in subsequent years, eventually reaching an elevation of 1,395 feet.

For 2026, the agency said lowering the reservoir could take approximately two weeks, followed by about two weeks at the target elevation, unless a major storm occurs. The Corps also said it would monitor water quality and coordinate with drinking-water providers and state officials about modifying, pausing or stopping operations if downstream turbidity threatens water systems.

Impacts from Green Peter remain central to the dispute. The Corps’ environmental review acknowledges that its earlier drawdown caused high turbidity and large losses of kokanee. The agency says Detroit’s phased approach and late-fall timing incorporate lessons from that operation.

Marion County maintains that the safeguards are insufficient and is also challenging the deeper Detroit Lake drawdown planned for fall 2027.