Federal agency that manages 13 Willamette Valley dams and reservoirs considering big changes

By ZACH URNESS/Salem Statesman-Journal

The U.S. Army Corps of Engineers is considering emptying Cougar Reservoir, scaling back hydropower and changing how it stores 500 trillion gallons of water in a new blueprint for managing 13 dams and reservoirs in the Willamette River Basin.

In a 2,200-page document released late last month, the federal agency laid out seven alternatives for improving conditions for endangered fish while managing a river system that brings drinking water, irrigation and recreation to Oregon’s most populous region.

The document, known as a draft Programmatic Environmental Impact Statement, took more than three years to complete and was last updated in 1980. It comes following years of lawsuits and court orders demanding the Corps retrofit dam operations to help native salmon and steelhead avoid extinction.

The Willamette Basin’s dams and reservoirs, which stretch from Cottage Grove to Detroit and include major rivers like the Santiam and McKenzie, were originally designed to reduce flooding. That main purpose won’t change.

But within its secondary operations, and in the document, the Corps proposes some dramatic actions.

Its “preferred alternative” — the option they’re leaning toward — includes fundamentally changing Cougar Reservoir and building multimillion-dollar structures to help fish pass through dams and regulate river temperatures. It includes scaling back hydropower, eventually scaling back hatchery fish programs and tweaking how much water is stored in the 13 reservoirs.

“This is a big deal,” Nicklas Knudson, acting project manager for the EIS revisions with the Corps, said. “What we’re doing now will be important for how we manage the system for the next 30 years.”

The release of the EIS sparks the beginning of a public comment period. Comments on the draft will be accepted through Jan. 19. They can be emailed to willamette.eis@usace.army.mil or mailed to PO Box 2946, Portland, OR 97208-2946.

Virtual public meetings will be held at 5 p.m. Tuesday and at noon Dec. 8. In-person public meetings will be held in early January including:

• 6-8 p.m. Jan. 9 in Springfield.
• 12:30-2:30 p.m. Jan. 10 in Eugene.
• 6-8 p.m. Jan. 11 in Sweet Home.
• Noon to 2 p.m. Jan. 12 in Stayton.

The meetings and comments are critical, officials said, because “this is the best chance to directly affect how we manage this system in the future,” Knudson said. “At this point, we can still make changes or transition away from the preferred alternative.”

There are things the Corps can’t change — such as the rule curve that governs when and how much total water the reservoirs can store — but just about everything else is on the table.

After the comment period closes, the Corps will take time to read and respond to comments, using them to shape a final decision expected late summer 2024.

“What makes this tough is that everyone comes to it from a different place — some people care about fish and environmental aspects, other people just want the reservoirs full, some people want to ramp up green power. It’s a multipurpose system that tries to do many different things,” Greg Taylor, the Corps’ fisheries biologist for the Willamette and Rogue basins, said.

Cougar Reservoir drawdown considered

Each of the seven alternatives in the EIS emphasizes a slightly different way to manage the system using actions, like drawing down reservoirs (which is cheaper), and building new structures, like temperature control towers and fish passage systems (which is more expensive).

In its preferred alternative — in this case Alternative 5 — the Corps proposed a mix of new structures and actions.

The most striking would be a major drawdown of Cougar Reservoir in the spring and fall that would allow salmon and steelhead to migrate through the bottom of the dam, giving access to better spawning habitat in the upper river while juvenile fish return downstream.

A main problem caused by the dams is that they block access to the best spawning ground for the fish, which are protected under the Endangered Species Act.

But while the extreme drawdown of Cougar is probably the best option for fish migration, it would mean “major adverse effects to reservoir recreation at this location,” the EIS said.

The drawdown would also mean less stored water in the Willamette system and require other reservoirs to release additional water to keep flows at normal levels for drinking water, irrigation and water temperature for fish. However, the early release of Cougar also means that some reservoirs, such as Detroit Lake, could fill more easily during dry springs.

“It could mean a slight decrease in the water level of the reservoirs in some years, but overall, I don’t think people would see much difference,” said Kathy Warner, environmental engineer and water supply specialist for the Corps. “In fact, in drier years, it could actually help some reservoirs fill.”

Another impact of the preferred alternative, according to the EIS, is reducing hydropower produced by the dams by 18 megawatts — roughly enough to power 14,334 households annually.

“There would be long-term, major, adverse effects on economic viability of power generation,” the EIS states.

Other parts of the alternative include building the long-debated fish passage system and temperature tower at Detroit Dam. In addition, it would add a new adult fish facility for upstream passage at Green Peter, and create a number of other structures.

This alternative costs $52 million per year, about middle of the pack in terms of cost compared to the alternatives.

“The Preferred Alternative improves fish passage through the (Willamette Valley System) dams using a combination of modified operations and structural improvements, along with other measures to balance water management flexibility and meet ESA-listed fish obligations,” the EIS states.

Corps officials stressed that while this is their preferred alternative, it’s not necessarily the one they’ll ultimately go with. In recent years, several major government projects were changed during the comment period away from a preferred alternative.

Other alternatives

The Corps laid out six additional alternatives that remain under consideration. Here is the basic idea for each alternative:

Alternative 1 would focus on storing more water to help cities and farmers with irrigation, produce more hydropower and aid recreation in communities behind dams like Detroit by having longer recreation seasons. It would also mean more water for downstream uses. But it would cost $104 million per year, twice what the preferred option would cost, due mainly to the number of structures that would need to be built while “resulting in fewer benefits to ESA species,” the report says.

Alternatives 2A and 2B are similar to the preferred alternative, including a mix of new structures and actions. The main difference is that it would not include drawing down Cougar Reservoir and instead construct a fish passage system with a floating fish screen in 2A. It would cost more at $67 million per year, but increase hydropower.

“The uncertainty that a (floating fish screen) would effectively collect juvenile fish migrating downstream at Cougar Dam – coupled with the high cost to design, construct and operate the facility, lead USACE to not select alternative 2,” the report states.

Alternatives 3A and 3B would bring the most significant changes to the entire system by using major drawdowns at multiple reservoirs each spring. Alternative 3A would reduce storage of the dams by 56% and would likely cause downstream water users such as cities and irrigators to be shut off in drier years. It also would decrease hydropower by 87 megawatts per year and it would impact recreation by having lower water elevation. The Corps estimates it could cause a 50% reduction in recreation-related jobs along the North Santiam River. Alternative 3B has similar effects, but not to Detroit Reservoir.

In Alternative 4, fish passage would be improved primarily with structures to help water quality and fish passage, and more stored water would be released in the summers and fall. But it would be the most expensive at $113 million per year.