Willamette Water Supply System Frequently Asked Questions

While there is enough water to serve our region today, we must prepare to meet future drinking water needs. Washington County is expected to grow 30% by 2050, and while water conservation is important, it doesn’t remove our region’s need for an additional water source. This project prepares the region for a shifting climate, changing surface water supplies, and a growing population.

The Willamette Water Supply System is one of the largest public water infrastructure projects in Oregon’s history. An additional water source and new infrastructure allow the region to more easily adapt to future challenges. The benefits of the program are:

• High-quality water. New infrastructure delivers water that is treated at a new, state-of-the-art treatment facility using the latest technology. 
• Ready for Growth. Washington County is forecasted to grow more than 30% by 2050. WWSS expands our region’s water supply options so residents have a reliable water source as the population increases. 
• Earthquake resilient. A major earthquake could compromise our drinking water systems. The new treatment facility, pipelines, and storage facilities are constructed to better withstand a large-scale earthquake and restore water services more quickly after shaking stops. 
• Adaptable.  Today, heat waves, stronger storm events, and wildfires are more common. New infrastructure and an additional water source help our region adapt to unforeseen climate challenges. 
• Locally Owned. Local ownership means local control. Washington County’s urban water agencies can operate independently to best serve local customers’ needs. 

Water quality in the Willamette River has significantly improved since the 1970s after the passage of landmark environmental legislation, including the Clean Water Act. 

Over several decades, the mid-Willamette River near Wilsonville has proven to be a high-quality drinking water source. For more than 20 years, the City of Wilsonville has trusted the river for their drinking water, which consistently meets or exceeds drinking water standards. 

The Willamette River is unique in that it flows south to north. Water for the WWSS is drawn at the intake facility in Wilsonville, which is 30 miles upstream (south) of the City of Portland. Further, Willamette Falls in Oregon City lies between the City of Portland and Wilsonville serving as a natural barrier between the two portions of the river.

"Water supply integration" refers to when new water is introduced into an existing drinking water system. In other words, treated Willamette River water will flow into TVWD's existing pipelines and be delivered to your homes.

All drinking water supplies have unique characteristics, and changes in supply may be perceptible to some, but not all, customers.

TVWD will begin delivering to customers as early as late-2026, taking a phased approach, meaning some customers will receive water from the new supply before others. TVWD will communicate with you before integration occurs. 

During integration, your home may experience temporary changes to your water’s taste, smell, or color as the new water replaces the water TVWD has historically served. These changes are temporary and will settle out after approximately two weeks with the new water supply. These changes are largely due to two factors: a different type of drinking water disinfectant and different water treatment and filtering processes between the Portland water and new Willamette Water Supply. 

Temporary Changes

• Slight changes in taste or odor: The water served to your home could have a different or noticeable, but safe, change in flavor or smell. It might taste or smell slightly different, like chlorine or minerals.
• Cloudy or discolored water: When water sources are mixed, it can cause harmless organic particles to become more visible. You might see a temporary cloudiness or slight discoloration, especially when taps are first turned on.
• Pressure fluctuations: Some customers might experience minor changes in water pressure as the water system adjusts.

Lasting Changes

• Subtle taste differences: Over time, the new water supply may lead to a permanent, but minor, change in the overall taste of your water due to the different water sources being served. This is a natural result of the new supply blend.
• Improved water quality: With more robust and reliable treatment, the overall quality of your drinking water may improve, offering better consistency and safety long-term.

Please note: homes built in the 1970s or older, with original home plumbing, are more likely to experience these changes to their water than newer homes or those with plumbing recently replaced. The higher likelihood of changes in older homes is due to the build up of organic materials inside your home's plumbing and fixtures over time in addition to the types plumbing materials commonly used in older homes.

Organic materials that build up inside older plumbing over time can be released by the change in water characteristics with the new water source. Older plumbing, specifically galvanized pipes, can cause temporary water discoloration in your home when the new water supply enters your home. 

The potential for lead to be released from plumbing joints or fixtures from this era is also possible. This can occur from materials that are no longer allowed per plumbing code but could still be used in homes from the 1980s or older, such as brass containing lead.

After years of study and analysis, the mid-Willamette River near Wilsonville was identified as the preferred choice for an additional water source. 

Several water sources were evaluated, including raising the dam at Hagg Lake, constructing new Columbia River groundwater wells, and purchasing water from other water agencies. After thoughtful analysis, the Willamette River was determined to be a high-quality water source that offers the most community benefits at the lowest cost when compared to alternatives. 

Visit our Long Term Water Supply Options Technical Memos page for more information.

TVWD's Board of Commissioners adopted ordinance 1-01 in 2001, requiring a public vote before Willamette River water could be served to District customers. However, the Board determined that satisfactory public debate and discussion about the Willamette River as a water source had occurred, and adopted ordinance 01-13, which repealed ordinance 1-01. Visit or Resolutions, Rules and Ordinances Web page to read the text of the ordinances.

This project represents a $1.6B investment in our region’s health and economic vitality. Project funding comes from a combination of loans, grants, reserves (savings), and customer rates. The cost of the project will be spread over decades, meaning future customers will help pay for the benefits, and costs are shared by all three project partners (TVWD and the cities of Hillsboro and Beaverton).

Project funding for TVWD's potion comes from low-interest loans, grants, TVWD's savings, and customer rates. Federal loan re-payment will be spread over decades, meaning current and future customers help pay for this project. TVWD has increased rates in past years to help fund project planning, engineering and construction, which is nearly complete. You can get the latest information about our rates at 2025-2027 water rates here. 

Project funding for the City of Hillsboro and City of Beaverton portions are available at their respective websites. 

Water will not be fluoridated at the Willamette Water Supply System water treatment plant, however, individual water providers may add fluoride when it enters their distribution system. For information on fluoridation for the three partner agencies, please contact them directly:

Tualatin Valley Water District

(503) 848-3000 | TVWD Fluoridation Website

City of Hillsboro

(503) 615-6702 | City of Hillsboro Fluoridation Fact Sheet

City of Beaverton

(503) 526-2222 | City of Beaverton Fluoridation Website

Water hardness will largely remain the same or decrease slightly when Willamette water replaces the existing Portland supply purchased by TVWD. Currently, water hardness is seasonally influenced when Portland mixes groundwater into their supply, which increases its overall hardness (expressed as grains per gallon or carbonate alkalinity). Once Willamette water is served to customers, this seasonal blend will no longer occur. This will result in consistently soft water, year-round. The Willamette supply is also comparable to TVWD's other source, the Joint Water Commission, which is also considered soft and will continue to serve TVWD customers. More information on current water hardness is available here. 

We understand the concern about data centers as more of them are being developed across our region. These facilities can use significant amounts of water depending on their size. However, in TVWD's service area, data centers are part of the commercial category and commercial customers make up 2% of our customers and use a small share of the total water we provide. Residential growth is outpacing commercial growth in our service area. Data centers pay for the water they use under the same rate structure as residents, plus system development charges which developers are required to pay TVWD when developing new buildings. Their usage is billed accordingly so that residential customers do not take on that cost burden. 

Please read our Data Centers and TVWD Water Use fact sheet for more information about data centers in TVWD's service area.