Lake Tapps (Washington)

Lake Tapps is a reservoir in Pierce County, Washington. It was created in 1911 by Puget Sound Energy and operated for hydroelectric power until it ceased power production in 2004. In December 2009 PSE sold the lake to the Cascade Water Alliance, a nonprofit corporation whose members are five cities (Bellevue, Issaquah, Kirkland, Redmond, and Tukwila) and three water districts (Covington Water District, Sammamish Plateau Water and Sewer District, and the Skyway Water and Sewer District). It provides water to almost 400,000 residents and more than 22,000 businesses. It plans to eventually use Lake Tapps as a municipal water supply source, but not until at least the 2030s or later.

Cascade has signed an agreement with the Lake Tapps homeowners that guarantees full recreational lake levels throughout the summer. It has also signed an agreement with the Muckleshoot Indian Tribe and the Puyallup Tribe of Indians to ensure instream flows for fish. The four cities that surround the lake, Auburn, Bonney Lake, Buckley and Sumner, worked with Cascade to ensure their future water needs will be met for about the next 50 years. Cascade is now the operator of Lake Tapps.

Lake Tapps is about 4.5 square miles (12 km2) in surface area and has about 45 miles (72 km) of shoreline. The local terrain is such that the shape of the shoreline is very complex, with many inlets, peninsulas, and islands. Before the reservoir was created there were several smaller lakes, including one called Lake Tapps. The reservoir is held in place by a series of dikes. The lake is also known to hold many fish including carp, smallmouth bass, perch, and tiger musky.

A diversion dam on the White River, near Buckley, Washington, routes water into a flume which empties into the east side of Lake Tapps. On the west side of the lake, water had originally been routed to the "Dieringer Powerhouse" to generate hydroelectricity, after which the water was returned to the White River, about 20 miles (32 km) downstream from the diversion dam. Although there will be no power generation, the water will still be diverted and returned to the river. The level of the lake is lowered from October to April for flood control purposes and aquatic plant management, rendering it unusable for recreation half of the year.

At the diversion dam on the White River is a fish trap, which catches salmon migrating upstream. The fish are driven by truck and released upriver of Mud Mountain Dam, which blocks salmon migration. This technique is called a "trap and haul system".

Lake Tapps is often considered its own city or census designated place, however the area surrounding the reservoir is part of the city of Bonney Lake, Washington, which in turn is a separate city from Sumner, Washington. At the northern edge of Lake Tapps is Auburn.