Latest CBB News | Archives | About Us | Free Newsletter




Latest CBB News
Spill Begins Late At Detroit Dam To Aid Wild Spring Chinook, Steelhead In North Santiam River
Posted on Friday, June 29, 2018 (PST)

Spill at Detroit Dam began last week, about three weeks later than normal. The spill is intended to warm the water in the North Santiam River downstream of Big Cliff Dam, Detroit’s re-regulating dam.


The change is to accelerate both the rate of emergence of wild spring chinook and winter steelhead fry below the two dams and upstream passage of adult chinook and steelhead, according to the U.S. Army Corps of Engineers, which operates the two dams.


Temperature control spill at Detroit began June 21 to create optimal spawning and rearing conditions of the spring chinook, listed as threatened under the federal Endangered Species Act, as well as for threatened Willamette River winter steelhead. Both emergence and adult migration have been slowed by the colder water released into the river from the bottom of the dams. Spill adds warmer water to those releases.


As of June 26, some 44 wild spring chinook and 152 winter steelhead have been counted at the Minto Hatchery, operated by the Oregon Department of Fish and Wildlife and located downstream of the dams.


“We timed the start of the spill operations to allow the City of Salem time to take water quality samples near Big Cliff Dam and to process and analyze the data prior to spill flow reaching the intake at the Geren Island water treatment facility,” said Salina Hart, Chief of the Corps’ Reservoir Regulation & Water Quality Section. The water treatment facility is owned by the City of Salem.


Spill at the dam to create a warmer river downstream normally begins June 1, but the Corps agreed to the delay to allow the City of Salem enough time to implement and train personnel on new equipment and treatment options designed to better test and prevent cyanotoxins from entering Salem’s water treatment facility, according to a Corps press release.


An algal bloom advisory at Detroit Reservoir that’s been in effect since June 15 was lifted this week, June 25, by the Oregon Health Authority, according to Corps’ spokesperson Richard Hargrave. He said that such a bloom is not uncommon this time of year.


Salem has been under some level of water advisory for much of June, including a week-long “do not drink” advisory for vulnerable populations, due to cyanotoxins in its drinking water. The reservoir’s toxic algae bloom is considered a source of the polluted water, according to a June 25 update from the City of Salem.


The Corps, NOAA Fisheries, Marion County, along with the cities of Salem and Stayton have been meeting regularly to talk about mutual operations with regards to public health and the Corps’ responsibilities associated with threatened salmon and steelhead.


Additionally, the Corps has developed a water quality monitoring plan during the temperature spill operations and will continue to provide test results to Marion County and the cities of Salem and Stayton, as well as provide water retention times in the Big Cliff reservoir, travel time to the City of Salem treatment facility intake, and daily operational release schedules.


Temperature modeling by the Corps’ water quality team found that delaying spill beyond June 21 would result in temperatures that may have “critical impacts” to spring chinook and winter steelhead.


“We ran several temperature models to look at the temperature impacts that additional spill delays would have; waiting will result in critical impacts to fish,” said Greg Taylor, a Corps fisheries biologist. “The delays we’ve already made have prolonged the time that steelhead fry emerge from the gravel by five to eight days and delayed chinook migration in the North Santiam by three weeks.”


Spilling some of the warmer water from Detroit Reservoir now is a way to preserve colder water for September and October, a time when water temperatures could exceed limits for spawning and rearing of chinook salmon, the Corps said. The spill operations do not increase the amount of water that is regularly released from Detroit Dam on a daily basis.


The target stream temperature downstream of the dams is a minimum of 50 degrees Fahrenheit and a maximum of 55 degrees F, Hargrave said.


Since 2007, a combination of spill and normal releases of water for hydropower generation from Detroit Dam has been used to approximate natural pre-dam North Santiam River water temperatures.


At full conservation pool, opening a spillway gate at Detroit Dam releases warmer water from a depth of about 20 feet below the surface of the lake, the Corps said. Cooler water from more than 150 feet below the surface of the reservoir is released when water passes through the hydropower turbines, allowing the production of electricity. Detroit Reservoir is nearly full, according to Corps information at


In spilling from the spillway and generating hydropower at Detroit Dam on a daily basis, warm and cold water mixes in the small pool between Detroit and Big Cliff dams and is continuously released from Big Cliff Dam to sustain North Santiam River flows within targeted temperatures.


In the future, the Corps may have another way to control water temperatures downstream of the dams, while it also aids juvenile and adult fish passage. Late last year, it said it is considering adding a $100 to $200 million water temperature control tower in the Detroit Reservoir.


The tower would aid downstream juvenile passage with attractor flows in the reservoir and it would help control discharge water temperatures downstream of Detroit and Big Cliff dams and beyond into the Santiam River system.


The Corps’ Portland District operates a system of 13 dams and reservoirs in the Willamette River Basin for power generation and flood control


Also see:


--CBB, February 23, 2018, “Corps Considers Mixing Tower At Detroit Dam, Would Be One Of Three In Oregon,”


--CBB, December 8, 2017, “Corps Seeking Public Input On Detroit Dam Fish Passage, Temperature Control Scoping Process,”


-- CBB, June 16, 2017, “Willamette BiOp For Fish: Four Subbasins Focus Of Corps’ Salmon Reintroduction Programs Above Dams”

Bookmark and Share


The Columbia Basin Bulletin, Bend, Oregon. For information or comments call 541-312-8860.
Bend Oregon Website Design by Bend Oregon Website Design by Smart SolutionsProduced by Intermountain Communications  |  Site Map