Lake Tapps Public Water Supply Project

This page is being maintained as an archive of past information and will not be updated.

The Department of Ecology has issued to Cascade Water Alliance (Cascade) four interrelated water rights and one water right change.  This completes a multi-year project to propose and develop a regional water supply system to meet the Central Puget Sound’s long-term municipal needs.

Report of Examination - Ecology's decision documents

On September 15, 2010, Ecology approved and posted the final Lake Tapps Public Water Supply Project reports of exams.  The final water rights decisions and related appendices are posted below for review. 

In the News

Comments Received on the Draft Reports of Examination

Draft decision reports were available for public review during a 45-day period between May 7 and June 30, 2010.  Ecology reviewed each comment and made some revisions to the reports of examination. The comments Ecology received are summarized in the following document:

Project Information

The project will help supply the long-range municipal water needs of the Central Puget Sound region, protect salmon and improve water quality, and assist ongoing efforts to preserve Lake Tapps. Ecology’s approval provides Cascade Water Alliance (Cascade) with four new water rights and one water right change.  These allow Cascade to store water in the Lake Tapps Reservoir, divert water from the White River into Lake Tapps to supply water for the Water Supply Project, and withdraw water from Lake Tapps for municipal water supply purposes. As currently proposed, the project will take 50 years to fully develop and gives Cascade the authority to take an average of 48 million gallons of lake water a day for public use.

The Cascade Water Alliance is a coalition including the Cities of Bellevue, Issaquah, Kirkland, Redmond, and Tukwila, the Covington Water District, the Sammamish Plateau Water and Sewer District, and Skyway Water and Sewer District. Cascade will construct the necessary water treatment and delivery systems to get water from the lake to its members.

Lake Tapps was formerly managed for power generation by Puget Sound Energy using the White River hydroelectric project, which created Lake Tapps.  PSE stopped hydropower operation in 2004 because of the costs of project operation associated with a Federal Energy Regulatory Commission hydropower license and recently sold the project to Cascade.

In 1980, Ecology adopted a rule that closed the White River to new water-right allocations.  Therefore, Cascade’s proposal had to demonstrate that it would significantly benefit the environment and the public. Cascade’s proposal had to also:

Cascade developed the necessary mitigation strategies and agreements to ensure White River flows and lake levels are protected and enhanced with feedback from Tribes, the Lake Tapps Community, Pierce County, nearby cities, and others.

Historical Background

Lake Tapps Reservoir, completed in 1911, is located in Pierce County. It is now owned and operated by Cascade.  Currently, private residences and public and private parks surround most of the reservoir, with many boat launch facilities and docks. Lake Tapps Reservoir offer many recreational opportunities for both residents and the public, such as boating, water skiing, fishing, and swimming.

The reservoir is a key component of the Hydro Project, which consists of a diversion dam located on the White River at the town of Buckley, an 8-mile flow line, an off channel storage reservoir (Lake Tapps Reservoir) and a powerhouse and tailrace canal that enters the White River below Auburn.  Although hydropower generation has ceased, these facilities remain and continue to be used to operate Lake Tapps Reservoir.

Under a vested surface water claim, water is diverted from the White River near the City of Buckley, conveyed to the reservoir through a flow line consisting of a series of channels and settling basins, and used to generate hydropower.  Approximately 20 cubic feet per second of the water is diverted from the flow line through a fish screen that prevents fish migrating downstream from entering Lake Tapps.

Water (and fish) diverted at the fish screen are returned to the White River several miles downstream of the diversion dam.  All other water, except for small amounts of leakage and evaporation, is ultimately returned to the Lower White River upstream from the City of Sumner.

Related Information Sources


Lake Tapps Water Supply Project

Southwest Regional Office
Department of Ecology
PO Box 47775
Olympia WA  98504-7775
Phone 360-407-6859