A planned 2026 drawdown of the Detroit Lake reservoir will increase turbidity on the Santiam River beyond what Salem’s primary water treatment plant can handle.
SALEM, Ore. — Salem City Council voted unanimously Monday to declare a state of emergency to help prepare its municipal water system for a planned deep drawdown of the Detroit Lake Reservoir in the fall of 2026. The city’s primary source of drinking water is a treatment plant on the North Santiam River about 27 miles downstream from the Detroit Dam.
The National Marine Fisheries Service ordered the deep drawdown late last year to try to improve salmon migration. The drawdown will stir up sediment built up behind the dam and cause increased turbidity levels in the North Santiam River, which could clog the Salem plant’s “slow sand” filtration systems, according to the city’s website.
“Conditions that are coming for us that we need to get ready for,” said Allen Dannen, an engineer for the Salem Public Works department. “We need to take action immediately and really that is to expand our alternate supply sources.”
The draft resolution on Monday’s city council agenda stated that Salem’s current alternative water sources “can only marginally meet demand,” during the drawdown the system would have little resiliency. The procurement process to add water sources would normally take until 2027, but the emergency will give the city manager authority to move faster.
Salem’s current alternative water sources include groundwater wells near the treatment plant, an Aquifer Storage and Recovery system in south Salem and emergency supplies from Keizer, according to the city’s website. Those three sources can supply a combined 22 million gallons per day, but Salem’s 200,000 ratepayers use about 24-25 million gallons per day.
“Even with the wells if we can get one-and-a-half gallons per well out of it, that margin is still really narrow,” Brian Martin, Salem’s Public Works director. “And if any one of those things goes, it could really be catastrophic.”
The emergency declaration and the website don’t mention any possible alternative sources other than building new wells. The website notes that Salem has a legal right to tap into the Willamette River for drinking water, but doing so would require a whole new treatment plant that couldn’t be built in time for the drawdown.
The deep drawdown will lower Detroit Lake to about 1,395 feet above sea level, which will be the lowest level the reservoir has seen since it was first filled in 1953, according to the city’s website, and about 55 feet below its typical fall season level. The lake’s full capacity is 1,565 feet above sea level.
The drawdown process will take 30 to 60 days, after which the lake will gradually refill from rain and snowmelt — but the U.S. Army Corps of Engineers will be required to repeat the drawdown during each fall salmon migration season for at least three years and study how the change impacts salmon populations.
Salem is the largest city impacted, but it isn’t the only one; the city of Stayton also draws its water from the North Santiam River at a treatment plant very close to the Salem facility, and the city’s mayor and council president sent a letter to the Army Corps of Engineers in June asking for the drawdown plan to be reconsidered.
The cities of Sweet Home and Lebanon filed a $37 million lawsuit against the Army Corps of Engineers last year over a similar drawdown of the Green Peter Reservoir in 2023, claiming that the project caused increased turbidity on the South Santiam River and damaged both cities’ water treatment systems.