Scoggins Dam at Hagg Lake
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, Clean Water Services (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.
A dry spring season and recent warm weather prompted CWS to begin releasing cool water, following the trend in the last 10 years of releasing water earlier than normal. "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 winter and spring has resulted in less water in streams and the river."
Knowing when and how much water to release is an intricate balancing act based on stream flow, 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, CWS and other groups 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 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 1970's 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 now controls nearly 20 percent of the stored water in the Tualatin River Watershed and is working with water managers to meet growing industrial, municipal, and environmental water needs.
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 over 600,000 residents and businesses in urban Washington County.
Government & Public Affairs Director
Clean Water Services