Water Releases Keep the Tualatin River Flowing

Hillsboro, OR

Scoggins Dam at Hagg Lake

The upper Tualatin River would be a mere trickle during dry months if not for life-giving releases of cool water from Hagg Lake and Barney Reservoir. Because the Tualatin River is a vital source of water for Washington County's abundant agricultural crops and growing population, scientists closely monitor the river to determine when more water is needed to sustain water quality, fish and wildlife. 

These annual releases typically occur in July when stream flows drop and temperatures increase. Following the trend over the last few years of releasing water earlier than normal, the recent dry, warm weather prompted Clean Water Services to begin releasing cool water in late May. "We have to release enough water now to cool the river and sustain flows in the summer and through the dry fall months," said Water Resources Analyst Jamie Hughes.

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, Clean Water Services and other groups helps determine when and how much water is released. Clean Water Services 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, Clean Water Services releases about 30 million gallons of water per day during the summer and dry fall months to cool stream temperatures, enhance water quality, and provide habitat for fish and wildlife. In order to improve water quality, Clean Water Services maintains sustainable base flows in the Tualatin River. By late summer, more than 70 percent of the flow in the lower Tualatin River is from Clean Water Services' water releases from Scoggins and Barney Reservoirs, and its two advanced treatment facilities in Hillsboro and Tigard. See the Tualatin River Flow Diagram (PDF, 585KB). 

Clean Water Services 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. Clean Water Services now controls nearly a quarter 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 nearly 600,000 residents and businesses in urban Washington County. 



Mark Jockers
Government & Public Affairs Manager
Clean Water Services
503.681.4450 (o)
503.701.4293 (m)

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