Judge: Lower Green Peter to help fish

Scott Swanson

Green Peter Reservoir will be lowered to historic levels this fall and early winter, during which period its dam generators will cease to produce electric power, in an effort to preserve young Chinook salmon and steelhead, a federal judge has ordered.

U.S. District Judge Marco Hernandez has approved a plan produced by an “expert panel” of scientists and others, which requires Green Peter to be drawn down to 780 feet above sea level, some 220 feet below full pool, by Nov. 15. Although this drawdown will not go to the historic river bottom, this will be the lake’s lowest point since it was completed in 1966.

Although the move will impact the dam’s ability to produce power, the biggest impact for the public will likely be the loss of the Thistle Creek and Whitcomb Creek boat ramps on Green Peter, which will be out of the water during the drawdown, which is expected to last into January.

The plan is a response to a September 2021 court order by Hernandez that the U.S. Army Corps of Engineers make changes at its dams in the Willamette Basin so that juvenile salmon and steelhead could pass through them more easily. Its stated goal is “to establish a self-sustaining population of spring Chinook salmon upstream of Green Peter Dam.”

Hernandez ruled that the Corps must change its dam operations in numerous ways to improve fish migration and water quality in four tributaries of the Willamette River, including the South Fork of the Santiam River, on which Foster Dam is located.

The “technical advisory team” that produced the plans, which consisted of two members designated by the plaintiffs, two National Marine Fisheries Service biologists, two Corps “dam-operations experts” and two “ad hoc” federal wildlife and/or geological experts, was created following Hernandez’s initial ruling to determine the restrictions with which the Corps must comply and how the outcomes of the measures implemented by the Corps will be evaluated.

The injunction required a deep drawdown of Cougar Reservoir on the South Fork of the McKenzie River and impacted spill operations at Foster Dam last fall.

“Deep drawdowns” require the Corps to lower the elevation of the reservoirs to within 25 feet or less of the dams’ regulating outlets, prioritizing water flow over the top of the dam rather than through hydropower turbines, especially during the night when fish have higher rates of migration.

The fish are listed under the Endangered Species Act and, according to environmentalists who have sued the Corps on multiple occasions over the last decade to gain information about dam operations and the health of fish populations, dams on the Willamette River have blocked access to spawning grounds, which has contributed to population declines.

Hernandez’s injunction is in response to a lawsuit filed in early 2021 by the Northwest Environmental Defense Center, Wildearth Guardians and Native Fish Society, arguing that the Corps should be more transparent about its dam operations and their impacts on salmon and steelhead smolts heading out to sea.

Hernandez, in his initial ruling in July 2021, chastised the Corps for fighting “tooth and nail to resist implementing interim fish passage and water quality measures that it was supposed to begin implementing a decade ago, and that National Marine Fisheries Service has been recommending for years.”

Saving Salmon and Steelhead

Concerns about the health of the region’s wild salmon and steelhead populations have prompted a variety of strategies, including recent efforts to down trees in local streams to improve nesting areas for fish. (See page 1.)

As stated in the Corps’ plan for Green Peter, in recent years, biologists have determined that juvenile Chinook salmon and winter steelhead best get past local dams when provided with a “near-surface” route, and tend to pass over dams mostly at night. Studies have also shown that young fish tend to survive better when they are not passing through power generator turbines.

The plan approved by Hernandez requires that back-up power by diesel generators be supplied to Green Peter to ensure that the dam’s operations can continue.

Having accomplished that, by 2023 at the latest, Green Peter will be drawn down to 780 feet, with flows between 1,500 and 3,000 cubic feet per second. Low pool this past winter, in December and January, was about 920 feet, according to USAC data.

Outflow volume at Green Peter vary by time of year. In the past week has been around 1,750 cfs, but it can range from 8,000 to 10,000 cfs in the winter to zero in the summer.

When lake levels drop below the minimum power pool, 887 feet, the powerhouse will cease operations, according to the plan.

Once the reservoir is at low pool, adult fish will be planted above the Green Peter dam and, the plan projects, “naturally produced juveniles” will begin to pass the dam during drawdowns starting in 2023. If available, according to the plan, “juvenile Chinook salmon raised for experimental purposes (surrogate fish) will be released at the head of the reservoir to evaluate reservoir and dam passage behaviors, and survival under the drawdown operation.”

Those fish, which will be trapped both above and below the dam, will be compared to natural fish in size and timing as they pass the dam, the plan adds.

The Oregon Department of Fish and Wildlife announced in early June that retention of Chinook salmon in Green Peter, Foster and Detroit reservoirs is prohibited through Oct. 31.

Chinook have been released above those dams. Retention of salmon is already prohibited in the streams above Green Peter.

According to ODFW, the rule is needed to protect hatchery Chinook adults as they are released above Green Peter Reservoir in response to Hernandez’s court order.

A large portion of the historical spawning habitat in the South Santiam sub-basin exists above Green Peter Dam, according to state officials. These hatchery fish and their offspring will be studied to determine the best option for salmonid passage and survival.

Low To No Flows

When the reservoir is refilled during the spring, “outflows could be very low, if not zero,” the plan states, and “refill timing may be adjusted.”

Powerhouse operation will resume once the lake is at 887 feet.

The deep-draft lowering of the lake will likely affect water temperatures below the dam, as the water coming out of the lake will be discharged through the dam from about 150 feet deeper than the spillway crest, which is at 968.7 feet.

USAC spokesman Tom Conning said that following the drought period in the summer of 2021, the reservoir elevation got down to just above 900 feet before the rains came.

The drawdown could result in colder water temperatures in the river and flowing into Foster, according to the plan.

“Sudden changes in outlet depth during the drawdown may cause abrupt changes in Green Peter discharge temperatures,” it states, adding that because the water will run through Foster Lake, water temperatures may be “smoothed.”

Power Generation Reduced

According to the plan, the operation “will severely reduce power generation” at Green Peter, starting in the summer, as the drawdown begins, and completing ceasing the production of electricity by mid-October, continuing through mid-January.

Green Peter Hydroelectric plant is located near the end of a transmission line and furnishes peak power to the local area, as far away as Albany.

Conning said that Green Peter is considered a “power peaking dam,” which provides extra power for the local network when there is extra demand, such as in the mornings or evenings, when people are getting ready for work or coming home.

“Green Peter is one of those we turn on to provide extra power,” he said. “When there’s a heat wave, we use the power peaking dams. When that peak ends, we don’t have to run the turbines.”

The plan notes that operations at the dam may be curtailed by the drawdown, since it will not be generating power once the lake level falls below 887 feet and “there is no control over the outlet works or the drainage pumps that prevent flooding in the powerhouse and dam” without power to the dam or powerhouse.

The dam actually has an emergency backup diesel generator, but the water level necessary to cool that equipment is 100 feet above the targeted elevation for the draw-down.

A temporary diesel generator will be installed at the powerhouse to supply emergency power, but it may not be in place right away, though the goal is to get it in this year and “no later than the Summer of 2023.”

Recreational Impacts

How the drawdown will affect recreation on the lake remains to be seen, said Linn County Parks Director Brian Carroll, who noted that he has yet to have an in-depth conversation with Corps officials about the plan. The county has invested heavily in developing camping facilities in the Green Peter area.

As far as recreation is concerned, boaters can use Whitcomb Creek Boat Ramp, on the northeast side of the lake, until the water level drops to 972 feet – “and it’s getting tight at 974,” Carroll said. Thistle Creek, located farther to the west, is accessible to 922 feet, he said.

“I’m hoping to have a better idea of what’s going on by mid-month,” Carroll said. “It’s going to depend on the amount of water in the lake. Until I get a little more information, it’s hard for me to know the repercussions for the summer and the future.”