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Utility begins Hagg Lake water release

FLOW - Project aims to improve water quality and protect fish
by: Courtesy Photo, A summetime water release project from the Hagg Lake spillway to the Tualatin River began July 1.

Clean Water Services began releasing water last Saturday from Scoggins Reservoir (Hagg Lake) to the Tualatin River in an effort to improve water quality and protect fish and wildlife by maintaining stream flows.

During the dry summer months, scientists at Clean Water Services monitor the water quality and flow of the Tualatin to determine when to release stored water from Scoggins and Barney reservoirs to restore river flows and protect the environment.

Scientists consider weather forecasts, the amount of stored water available in the reservoirs and the number of summer days left before requesting the release of water to the river. The goal is to augment flows to cool water temperatures and maintain dissolved oxygen levels that protect the fish and wildlife in the river, according to Tom VanderPlaat, water supply project manager.

'It's a delicate balancing act,' VanderPlaat noted. 'We need to release water now to cool the river, but we also have to hold back enough water to release during the drier months of September and October.'

Clean Water Services uses a cadre of water quality monitors, flow meters and weather data to make daily decisions on reservoir releases. The district's goal is to maintain the average summer Tualatin River flow above 150 cubic feet per second (CFS) at Farmington Bridge downstream from Hillsboro.

In July and August, the release rate will average 35 CFS or 23 million gallons a day. During the drier months of September and October, releases from Scoggins Reservoir will increase and releases from Barney Reservoir will start resulting in an average of 70 CFS or 45 million gallons a day.

Water released from the reservoirs supplement the river flows in the summer because the Tualatin River does not receive water from mountain snow melt.

Clean Water Services was one of the original investors in Scoggins Reservoir when it was built in the early 1970s to meet agricultural irrigation and drinking water needs. In the 1990s, the district joined the Joint Water Commission to expand Barney Reservoir on the upper Trask River to secure additional stored water.

During the late summer months, Clean Water Services' water releases from Scoggins Reservoir, Barney Reservoir and its two advanced wastewater treatment facilities account for more 50 percent of the flow in the lower Tualatin River. Clean Water Services is the sanitary sewer and surface water management utility for more than 480,000 people in urban Washington County and small portions of Multnomah County, Clackamas County, Lake Oswego and Portland.

The district operates four wastewater treatment plants, constructs and maintains flood management and water quality projects and manages flow in the Tualatin River to improve water quality and protect fish.