Clean Water News & Stories

Water Releases Keep Tualatin River Cool and Flowing

The arrival of warmer weather and the dry and hot forecast ahead prompted Clean Water Services to begin releasing cool water on June 22, 2022. 

The Tualatin River is a vital source of water for Washington County communities, crops and companies. To keep the Tualatin River flowing and healthy in dry months, CWS releases cool water from Hagg Lake and Barney Reservoir. Scientists closely monitor the river to determine when more water is needed to sustain water quality and ecology of the watershed. 

Thanks to a cool and wet spring, this year’s releases are unusually late, especially compared to last year, when CWS began releases on May 3 — the earliest in its history.

“Our region has seen record-setting rainfall the last few months,” says Water Resources Manager Raj Kapur. “While extremes in both directions are expected in the face of climate change, forecasts for this region predict we’ll predominately see longer, drier, and warmer summers, which will place greater burden on water resources. We are certainly seeing that over the last decade, with this year as an outlier.” 

Knowing when and how much water to release is an intricate balancing act based on stream flow, irrigation and water supply withdrawals, weather, water quality conditions in the Tualatin River, and the amount of water in the reservoirs. A network of continuous monitoring data from United States Geological Survey, Oregon Water Resources Department, and CWS helps determine when and how much water is released. CWS coordinates with the Joint Water Commission (which provides drinking water to several cities in Washington County including Hillsboro, Beaverton and Forest Grove), Tualatin Valley Irrigation District and the Oregon Water Resources Department to maintain stream flow. 

In an average year, CWS releases about 30 million gallons of water per day to maintain sustainable base flows, cool temperatures, enhance water quality and provide habitat for fish and wildlife. By late summer, more than 70 percent of the flow in the lower Tualatin River is from CWS’ water releases from Scoggins and Barney Reservoirs, and its water resource recovery facilities in Forest Grove, Hillsboro, and Tigard. See the Tualatin River Flow Diagram (PDF).

CWS was one of the original investors that built Scoggins Dam in the early 1970s for agricultural irrigation, drinking water, and flow enhancement. With the Joint Water Commission, it expanded Barney Reservoir in 1998 to secure additional stored water. CWS has access to 20% of the stored water in the Tualatin River Watershed. The stored water is used to enhance stream flow, provide habitat, and improve water quality in the Tualatin River Watershed. 

Everything we do at Clean Water Services aims to protect public health, while enhancing the natural environment of the Tualatin River Watershed. Combining science and nature, we work in partnership with others to safeguard the river’s health and vitality, ensure the economic success of our region, and protect public health for more than 600,000 people in urban Washington County. Although Clean Water Services maintains a close working relationship with Washington County government, it is separately managed and financed. 

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