Tualatin Basin Water Supply

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About the project


The Tualatin Basin Water Supply Project Partnership was authorized by Congress in 2004 to design and secure Washington County's water supply, respond to anticipated climate change and drought cycles, and meet the 50 year supply needs for water quality and critical habitat improvements in the Tualatin Basin.

Scoggins Dam is the central component of Washington County’s water supply and a major regional asset. It uses water from Hagg Lake to support more than 250,000 jobs, provide drinking water for nearly 400,000 residents, irrigate 17,000 acres of cropland, and sustain water quality in the Tualatin River to protect fish and wildlife habitats

Currently, Clean Water Services (CWS) and the Bureau of Reclamation (Reclamation) are partnering to preliminarily address the seismically at-risk dam and how to potentially develop additional future water supplies for Scoggins Dam. The partnership between the agencies, the first of its kind in the country, is developing a more detailed understanding of various options. This is called the Tualatin Basin Dam Safety and Water Supply Joint Project – or, “Tualatin Basin Joint Project” for short.

Frequently Asked Questions

>Why not restrict water usage so we don’t need to expand our water supply?
Conservation alone is not enough to meet the future demands for water. Especially in Washington County where homes and businesses are using 15% to 20% less water than a decade ago with effective water conservation programs and newer low water use appliances. This project addresses both water needs and urgent earthquake risks.
>To eliminate the earthquake risk, why not drain Hagg Lake or remove Scoggins Dam?
In our region 400,000 residents, 250,000 jobs and 17,000 acres of agriculture rely on the water stored in Hagg Lake. It is the water source for homes, farms and businesses throughout the Tualatin Valley, and currently the only source of water for City of Hillsboro. Life-giving releases from Hagg Lake keep the Tualatin River flowing in the dry months, and Hagg Lake is a thriving recreational asset.
>Who is paying for this and how much will it raise my water bill?
The U.S. Bureau of Reclamation will fund the dam safety aspects of the project, and 15% of the seismic improvement costs will be repaid by the local partners that share the water in Hagg Lake (Tualatin Valley Irrigation District, Clean Water Services, Lake Oswego Corporation, and the Cities of Hillsboro, Beaverton and Forest Grove).