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Willamette River Basin Review Feasibility Study

The Portland District of the U.S. Army Corps of Engineers and the Oregon Water Resources Department are jointly sponsoring a feasibility study to determine if and how space in the reservoirs can be reallocated during the spring and summer to provide stored water for municipal and industrial water supply, irrigation, and fish and wildlife uses.

It is a goal of the study to determine if current and future demands can be met in a cost-effective manner while considering those aspects of current operations that people value today.

Contact Us

To add your name to the project mailing list, provide a comment or ask a question, please contact one of the sponsoring agencies:

U.S. Army Corps of Engineers
503-808-4510

Oregon Department of Water Resources
503-986-0874

Email us

The Corps and the Valley

The Corps operate 13 dams and reservoirs in the Willamette Basin. Their primary purpose is to reduce the risks from flooding to people and property downstream during the winter months.

The dams also store and release water for other Congressionally authorized purposes, including hydropower generation, irrigation, water quality, supporting fish and wildlife and recreation. There is not a specific amount of reservoir space allocated for a particular use. This joint-use allocation is unique to the Corps' Willamette Valley dams.

Basin water demands increase

The Willamette Basin is Oregon's largest river basin. It contains nearly 70 percent of Oregon’s population, its most highly productive agricultural land, and significant habitat for anadromous fish populations. 

The Willamette River and its tributaries make it possible to support today's population and generate hydropower. The vast majority of people in the basin are supported by municipal and industrial public water systems that meet basic human needs, provide fire protection, and support business and industrial development. In communities near the reservoirs, recreational uses are an important contribution to local economies.

Willamette water also supports agricultural productivity and a healthy natural environment. Irrigation enhances the role that agriculture plays in Oregon's economy and keeps farming as a feasible vocation for future generations. Fish and wildlife require access to clean water to support all aspects of their life cycles.

Because water is so important to every resident of the basin, and to other Oregon residents who rely on a strong Willamette Valley economy, the stewardship of its water resources is critical to Oregon's future.

Population growth, increasing development, expanding irrigation and the listing of threatened or endangered fish species have created demands for increased water supplies in the Willamette Valley.

Future water supply options in the Willamette River basin are constrained by existing state and federal laws. For example, access to new surface 

water rights in sections of the mainstem Willamette River and most major tributaries is limited to a small set of uses to protect existing water rights and public instream uses. Groundwater is also limited or restricted in several areas of the basin.

The Study

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The State of Oregon has long identified the Corps' Willamette reservoirs as a new source of water for meeting current and future needs in the basin. Over the past two decades, numerous state and local agencies and other groups have discussed how the water stored in these reservoirs might be allocated specifically to help meet these future needs. 

Specifying a set amount of space for a specific purpose (such as irrigation or municipal and industrial use) requires the Corps to conduct a Feasibility Study through a formal, standard process. Congress must then authorize, or approve, recommendations resulting from this process.


The study will determine if future demands can be met in a cost effective manner while considering those aspects of current operations that people value.

The study also will consider how to meet the needs for ESA-listed fish, how to minimize negative impacts to existing reservoir and downstream recreation users, and how to minimize impacts to hydropower generation.

The environmental, social and economic impacts of the alternatives will be evaluated as required by the National Environmental Policy Act in an integrated feasibility study report/environmental assessment document.

Any reallocation as a result of this study cannot impact the Corps’ flood risk management mission. The Corps will not change the water control diagrams that indicate when and how water is stored and released to reduce flood risks. The Corps must also retain its ability to meet flow requirements for fish and wildlife. This study is focused on the spring and summer seasons, when stored water is available for downstream uses.

If the study results in an approved plan to distribute stored water to new municipal and industrial uses within the basin, the Corps and the State of Oregon will need to formulate a process for administering a new water contracting program in the basin. During the feasibility study, the agencies will examine what institutional arrangements are needed to carry out such a program. The new program also would apply to the release of stored water to meet downstream instream flow needs for fish and wildlife.




The Corps and OWRD intend to make reallocation decisions based on real, data-verified demands and other technical information. The Corps is collecting information on current and estimated future water needs from planning documents that municipal water suppliers submit to the Oregon Department of Water Resources. The agencies are evaluating all sources of water supply expected to be available for municipal, industrial and irrigation purposes and fish and wildlife enhancement.

The Oregon Department of Agriculture is providing information on irrigation needs and the 2008 Willamette Project Biological Opinions are the source for fish and wildlife flow requirements.

Demand data accounts for variation in needs by season and the availability of storage only during the conservation season (May through October). Demand projections consider factors such as population growth, water conservation actions and climate change impacts.

With the demand data and future projections of water needs, and considering input received from interested public and stakeholders during the Scoping phase of the Feasibility Study, the Corps and OWRD will consider a combination of supply and operational factors to draft reallocation alternatives for detailed review.

Alternatives will consider specific measures that can either work alone or be combined with others to form an alternative. A measure can be a feature (such as a structural element that requires construction or assembly on-site), or an activity (such as a nonstructural action) that helps meet study objectives.

Input from the public also will inform the analysis of potential impacts of reasonable reallocation alternatives as evaluated under the National Environmental Policy Act (see Get Involved).

Measures and alternatives will be screened using criteria developed in the early stages of the study. These criteria will ensure that recommendations contribute to meeting study goals and resolving the problems and needs that the study was initiated to address.


Input at key points in the Willamette River Basin Review Feasibility Study from Tribal, federal, state and local governments, public and private organizations, individuals and community groups is key to identifying ways to meet the demands for water while considering those aspects of the current system that people value today.

March 15-16 Scoping Meeting Presentations

Scoping is an opportunity early in the feasibility study to collect information and receive input from interested public and stakeholders on issues to consider in meeting future needs for municipal and industrial water supply, irrigation and fish and wildlife uses. This input will inform the analysis of potential impacts of reasonable reallocation alternatives as evaluated under the National Environmental Policy Act. At this stage, the Corps and OWRD also seek input on criteria for evaluating and comparing alternatives that help meet project goals.