During the summer season, which typically runs from June through October, lack of rain causes the natural water level in the Tualatin River to drop. As the level drops, Washington County’s Watermaster orders river water users to cease using river flow as a source. Who gets ordered off when is based on the river level and the age of the water right held – the oldest water rights are allowed to continue use the longest. Hillsboro, one of the JWC agency members, owns some of the oldest natural river rights on the Tualatin River, but even those usually only last until mid-June.
As the natural river rights dry up (literally), the JWC begins releasing water from two reservoirs to provide supplemental water in order to meet customer demands. Both reservoirs were designed to catch and store heavy rainfall in the winter months.
The Barney Reservoir is municipally-owned and operations are overseen by the Barney Reservoir Joint Ownership Commission (BRJOC). The BRJOC was formed in 1994 and includes one representative from each member agency of the JWC and also a representative from Clean Water Services. The reservoir is owned jointly by Tualatin Valley Water District (35%), City of Hillsboro (31%), City of Beaverton (21.5%), Clean Water Services (10%) and the City of Forest Grove (2.5%). In addition to municipal and industrial water supplies, 15 percent of the water is dedicated to flow enhancement of the Trask River and fish habitat.
The Barney Reservoir was completed in 1970 by the City of Hillsboro to provide the city’s municipal and industrial water. The original capacity was 4000 acre feet, and the dam was 1600 feet above sea level. The cost of construction was approximately $2.5 million. A 36-inch pipeline 6,500 feet in length was constructed to divert water from the Trask River to the Tualatin River, at a cost of $400,000.
Barney Reservoir is named in honor of J.W. Barney, Hillsboro’s first city manager, who was instrumental in the planning and construction of the original dam. The dam itself is named the Eldon S. Mills Dam in honor of Hillsboro’s second city manager, who was also the project manager for the Barney Reservoir Expansion project that was completed in 1999.
The $28.5 million expansion project spanned five years and increased storage capacity fivefold. The reservoir now holds 20,000 acre feet, with the dam at 1640 feet above sea level. It took 760,000 cubic yards of rock to form the backbone of the dam expansion.
Scoggins Reservoir (Hagg Lake)
Scoggins Dam and Reservoir was constructed in the l960’s and is owned by the Bureau of Reclamation. Its primary purpose was to provide flood control for the Tualatin Valley, but it also impounds 53,000 acre feet of water on Scoggins Creek. The majority of impounded water is owned by the Tualatin Valley Irrigation District, but the JWC has rights to use 13,500 acre feet of the impoundment when it fills to capacity.