Overview
Lake Washington is a roughly 21,600-acre natural lake bordering Seattle, Bellevue, Kirkland, Renton, and Mercer Island in King County. Since the 1916 opening of the Lake Washington Ship Canal, its outlet level has been regulated at the Hiram M. Chittenden (Ballard) Locks by the U.S. Army Corps of Engineers, Seattle District. Before the Ship Canal, the lake drained south through the Black River; the Cedar River is now the dominant inflow.
Average depth is about 108 feet and maximum depth about 214 feet, with on the order of 50 miles of urban and park shoreline. Deep open basins, floating bridges, and developed waterfronts define one of the Northwest's most intensively used urban lakes. Mercer Island and floating bridges divide the lake into distinct north and south basins for boaters.
The lake supports salmon, trout, bass, and other fisheries managed by the Washington Department of Fish and Wildlife, plus heavy recreational boating. City and county parks, marinas, and public launches provide access around the basin. City parks from Seward to Juanita and Kirkland waterfronts make this one of the most accessible urban lakes in the U.S.
Corps lock operations hold the lake in a narrow band - commonly near 20-22 feet on the project gage - rather than a deep flood-storage drawdown. Even small changes affect ship-canal navigation and docks, so monitoring current lake levels remains useful year-round. Lock operations also pass salmon and maintain a freshwater/saltwater barrier critical to the Ship Canal fishery.
Current Conditions
Lake Washington is currently 1.57 feet below full pool and has fallen slightly over the past week.
- 7-day trendFallingLatest movement can differ from the seven-day trend.
- 7-day changeDown 0.16 ft
- 30-day changeDown 0.60 ft
- Drought conditionsAbnormally Dry
About This Lake
Learn how this lake is managed, what affects its water level, and where Lake Insights gets its data.
Lake Washington is a 21,600-acre reservoir on the Cedar River managed by USACE Seattle District (Hiram M. Chittenden / Ballard Locks).