Lake Oswego’s source of water originates in the Clackamas River watershed. This high-quality water source receives runoff and snowmelt from a 940 square mile area located on the western slopes of Ollalie Butte, near Timothy Lake, in the Mount Hood National Forest.
Water is withdrawn from the Clackamas River, then pumped through a large-diameter pipeline buried beneath the Willamette River, to the Lake Oswego Tigard Water Partnership’s treatment plant in West Linn. Here, water is treated to exceed drinking water standards, before being pumped to the Waluga Reservoir site, and through the city’s distribution system, comprising 16 storage reservoirs, 13 pump stations and about 210 miles of water mains.
Since 1968, Lake Oswego's drinking water source has been the Clackamas River. In the early 1970's, Lake Oswego began supplying water to Tigard under a surplus water agreement, but as Lake Oswego's demands grew, the availability of surplus water decreased and Tigard began purchasing water from Portland. With the Partnership's expanded water supply system now complete, Tigard ended its supply agreement with Portland and receives all of its water from the Clackamas River.
The Clackamas River is one of Oregon's high-quality drinking water sources and is afforded special protection under state law. The Clackamas River watershed provides drinking water for more than 400,000 Oregonians in several other communities in North Clackamas County.
The Lake Oswego Tigard Water Partnership supplies water to more than 90,000 customers within the Lake Oswego and Tigard Water Service Area, including the cities of Durham and King City, and two-thirds of Tigard. The City of Lake Oswego also supplies water to wholesale customers including the city of Portland, and the Lake Grove, Glenmorrie, and Skylands Water Districts.