The Portland District, U.S. Army Corps of Engineers (USACE) takes care of 13 multipurpose dams, reservoirs, and fish hatcheries across Oregon's Willamette River Basin. Together, we call these the Willamette Valley System.

What We Do

Our job is to:

• Reduce flooding by holding back high-water events
• Store and release water for cities and farmers who need it for drinking, watering crops, and businesses
• Make sure rivers and streams have enough clean water for plants and animals
• Improve water quality in rivers downstream of our dams
• Provide opportunities for lake recreation that supports local businesses
• Generate electricity as water flows through the dams
• Support fish and wildlife habitat at our projects and in the rivers below

Keeping Everything Working

We maintain the system to keep it in good condition. We also adjust how we operate the system when:

• Weather patterns change
• City or agricultural water use changes
• We learn new things about how our dams effect the environment
• Technology improves
• Laws change, like new plant and wildlife protections under the Endangered Species Act (ESA)
• Congress directs us to

Following the Law

When we need to make notable changes, the National Environmental Policy Act (NEPA) requires us to:

1. Look at different ways to make these changes
2. Study how changes might affect people and the environment
3. Share this information with the public and get feedback

We document the environmental review in an Environmental Impact Statement. For more information on the NEPA process, check out the Citizen’s Guide To NEPA.

Why We Need Updates Now

We completed our last environmental review of the entire system in 1980. Since then, we've made many changes to help endangered fish, made improvements to the dams, and optimized operations for fish passage and improved water quality. Until now, we reviewed these changes one dam at a time—not as a complete system. We also have new information about how our operations effect the environment. For these reasons, we prepared an Environmental Impact Statement (EIS) to investigate how we'll continue to operate and maintain the Willamette Valley System under the changed conditions.

This EIS examines different ways we could adjust our operations and how these changes would affect people and the environment. We call these different approaches "alternatives."

We've only considered alternatives that allow us to continue all our Congressionally authorized purposes:

• Flood risk management
• Water supply
• Water quality
• Fish and wildlife protection
• Recreation
• Hydropower generation

Each alternative must protect endangered species listed under the Endangered Species Act (ESA). After analyzing a large range of options, we identified our preferred alternative for future operations. The public reviewed and commented on the Draft EIS and our preferred alternative in 2022, during an official comment period. We addressed these comments and updated the EIS based on feedback from the public, Tribes, and federal and state agencies.

Complying with the Endangered Species Act

Before we can decide to implement the preferred alternative proposed in the EIS, we must ensure our plan protects endangered species and won't put them at greater risk of extinction. To do this, we must consult with two federal agencies: the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS), together known as the Services. The ESA consultation process is not a public process like NEPA.

Under the ESA, the process is called Section 7 consultation and entails the following:

1. NMFS and USFWS review our proposed action, based on our preferred alternative in the Draft EIS, and provide Biological Opinions that states whether our plan is safe for endangered species.
2. If the Services determine our plan might harm endangered species, they'll require alternative actions to take to protect them.
3. We then update the Final EIS to include these protective actions.
4. We issue a NEPA Record of Decision that documents our decisions on the preferred alternative in the Final EIS and describes how our action complies with the ESA.

We received NMFS’ final Biological Opinion on December 26, 2024. Consultation with USFWS is ongoing.  

On January 4, 2025, Congress signed into law the Water Resources Development Act of 2024 (WRDA 2024). Section 1326 prevents us from completing our overall review of operations and maintenance of the system and consultation with federal agencies, until we prepare and formally analyze an alternative that ends federal hydropower operations in the Willamette Valley. To do this, we will supplement (add to) the EIS.

On April 11, 2025, we released the Final EIS and will shortly issue a Record of Decision outlining how we will operate the Willamette Valley System in compliance with terms of the 2024 NMFS Biological Opinion, until we finish the supplemental EIS required by Congress.

By releasing a Final EIS and issuing a decision now, we will comply with NEPA requirements for continue operations for improved fish passage and water quality while we assess the new WRDA 2024 requirements. 

We plan to complete the supplemental EIS in early 2026. The supplemental EIS will result in a long-term decision for how the Corps will operate and maintain the Willamette Valley System in 2026 and beyond.  

Detroit Dam Operations While We Prepare the Supplemental EIS

In 2025, we will not perform the deep fall drawdown for fish passage at Detroit Dam as we have not analyzed its effects. The 2024 NMFS Biological Opinion requires us to implement the drawdown for fish passage and is deeper than previous fall drawdowns. We will analyze the effects of the drawdown in the supplemental EIS. Until we complete the supplemental EIS, we will carry out water quality and downstream fish passage operations like we have done over the past few years. We do not anticipate a deep reservoir drawdown at Detroit Dam until fall of 2026.

We are working with NMFS to develop the timing and duration of the deep fall drawdown at Detroit Dam and considering potential impacts to communities and water quality. We will ask for public comment on the drawdown as a part of the supplemental EIS process.