Scoggins Dam at Hagg Lake
A dry spring season and the warmer weather ahead have prompted Clean Water Services to begin releasing cool water, following the trend in the last 10 years of releasing water earlier than normal. Releases began May 3, 2021.
The Tualatin River is a vital source of water for Washington County communities, crops and companies. To keep the 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, fish and wildlife.
"This is the earliest we've started releasing water in more than 40 years," said Water Resources Manager Raj Kapur. "The only source of water in the Tualatin River Watershed is rainfall, so the dry spring has resulted in less water in streams and the river. Climate change impacts forecasted for this region predict longer, drier and warmer summers, which will place greater burden on water resources. We are certainly seeing that over the last decade."
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 a 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 advanced treatment facilities in Forest Grove, Hillsboro and Tigard. See the Tualatin River Flow Diagram (PDF, 2MB).
CWS was one of the original investors that built Scoggins Dam in the early 1970s for agricultural irrigation, drinking water, and flow augmentation. 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.
For more than 50 years, Clean Water Services has worked to protect public health, while enhancing the natural environment. Combining science and nature, we clean water and return it to the Tualatin River, so it can be used again. More than 620,000 customers enjoy clean water and healthy rivers and streams as a result of our innovative water management solutions, drainage management, water-quality and stream-enhancement projects, habitat protection and more.
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Clean Water Services