By Benny Westcott
Lebanon Local
U.S. Army Corps of Engineers park ranger Christie Johnson outlined at an April 28 Lebanon Chamber of Commerce forum lunch how Green Peter Reservoir will be drawn to its lowest-ever level this year, beginning in June.
The goal was established by a 2021 U.S. District Court for the District of Oregon injunction to increase juvenile spring Chinook and steelhead salmon survival, as well as passage through the reservoirs and past the dams.
Drawdown operations will reduce Green Peter to a surface elevation of 780 feet, about 120 feet lower than it’s been since the Green Peter Dam was built in 1966. This will take place gradually but consistently over the summer to reach the necessary levels.
The reservoir is expected to reach its target elevation in early or mid-November. The Corps will then maintain levels at those elevations for one month. While the typical season to refill reservoirs begins Feb. 1, the group will begin filling Green Peter to normal winter flood risk elevations Dec. 16 to offset the drawdowns’ impact.
The 2021 injunction required the Corps to improve fish passage and water quality at several Willamette Valley Project dams for the benefit of Upper Willamette River spring Chinook salmon and winter steelhead salmon, both of which are listed as threatened under the Endangered Species Act. The Corps is working with the National Marine Fisheries Service, U.S. Fish and Wildlife Service, Bonneville Power Administration, and U.S. Bureau of Reclamation to implement the measures.
According to Johnson, the injunction basically told the Corps “We have to do more, and we have to do it now.”
“We are doing what we can to help these fish populations that are potentially in jeopardy of going extinct,” she said.
As part of their life cycle, Chinook and steelhead salmon hatch in the river’s freshwater before migrating downriver to the ocean, where they stay several years before returning. Green Peter Dam plays a part in blocking their routes.
“Salmon are surface-oriented fish, so we’re hoping they’ll key into the increased surface outflows from the reservoir [during the drawdown] and swim downstream, where they need to go,” said Kathryn Tackley, a physical scientist at the U.S. Army Corps of Engineers, Portland District, in a news release earlier this month.
According to biological opinions issued in 2008 by the National Marine Fishery Service and U.S. Fish and Wildlife Service, the Corps needed to do more to help endangered fish. So the agency aided in getting adult fish upstream to spawn in tributaries as well as helped move baby fish downstream.
“Protecting fish is not new,” Johnson said.
“We’ve been doing this for all the time that I’ve been here and working on finding ways to help fish species that are on the endangered species list.”
Last year the Corps executed a deep drawdown at Cougar Reservoir east of Eugene.
While protecting fish isn’t new, the historic drawdowns are anything but old hat for the Corps.
“This is all new to us,” Johnson said, “and we’re working really hard on coming up with a plan.”
She outlined a number of expected impacts. For starters, the Thistle Creek Boat Ramp at Green Peter will likely become unusable in late August or early September through December or perhaps January.
“I think there’s not that many people who use that boat ramp,” she said, “but they’re very passionate about wanting to be able to use that ramp, so I know it’s going to be disappointing to them to not be able to use the reservoir in the winter like they usually do.”
The drawdown will expose portions of the lake that haven’t been seen since the dam was built more than a half-century ago, and limited boat access may shift boaters and cause potential overcrowding at Foster Lake.
Johnson said the move may reduce the number of fish in the reservoir but added that, according to a Corps fish biologist, if the reservoir’s Kokanee population is reduced, the remaining Kokanee could grow larger.
Lack of boat access may make it more difficult for search-and-rescue teams to conduct rescue operations. Furthermore, visitors could get stuck in the soft mud that once was covered in water.
The Corps is also concerned about resources like old pioneer foundations and Native American sites being exposed.
Many cultural and historic resources are exposed every year, but the drawdown could increase that. Collecting cultural resources is illegal, Johnson noted. Vegetation and fish and wildlife could also be impacted.
According to Johnson, the extreme drawdown will happen this year and next year “for sure.” After that, there’s some uncertainty.
In her presentation, Johnson also shared some basic facts about the Willamette Valley water system and its dams. The Willamette River Watershed is roughly 750 square miles in all.
Johnson said that much flooding took place before the dams were built. Portlanders adapted to seasonal flooding by building makeshift bridges and rowing boats through town. Nowadays, 13 dams are all operated as a single system to manage that.
“But after a while, as more and more people moved into these big cities, the damage caused by that seasonal flooding was just so much,” she said. “It was just disastrous. People’s homes, businesses and farms were getting flooded almost every year. Something had to be done about it.”
In 1936, Congress passed the Flood Control Act, which authorized the U.S. Army Corps of Engineers to study the Willamette Basin’s flood problems.
That led to the authorization of funding for the first seven dams and reservoirs in 1938.
“The dams began construction in 1940, with the last of the 13 concluding in 1969. All are now more than 50 years old, Johnson said, “but still in great shape.”
While their primary purpose is flood risk management, the dams are authorized for others as well, like navigation, water quality, irrigation, water supply, recreation, and environmental stewardship.
Nine have hydropower plants, which provide renewable energy.
“If they’re all running at the same time, they supply enough energy to power 300,000 homes. According to Johnson, these dams make electricity in Oregon less costly than in other states.
She added that the dams prevent more than $1 billion dollars in flood damage every year.