Lake Washington borders the eastern side of Seattle. The lake is Washington's second largest natural lake, covering 21,500 acres and reaching a maximum depth of 214 feet. Lake Washington drains westward through Lake Union and the Ship Canal to Shilshole Bay in Puget Sound via the Ballard Locks.
Lake Washington is an important natural resource for navigation, recreation, and fish and wildlife habitat. The lake shoreline serves as an important rearing area for threatened juvenile Chinook salmon, as well as supporting many other aquatic and wildlife species.
Lake Washington is fed by high quality water from the Cedar River, however, there are concerns about pollutants such as fertilizers, pesticides, petroleum products, and bacteria reaching the lake. High fecal coliform bacteria levels can cause swimming beach closures to protect public health. The lake is bordered by extensive bank armoring, docks and piers, and little native shrubs and trees, which lead to relatively poor habitat for fish and wildlife.
Areas of Seattle that drain to Lake Washington are divided into the North, Central and South Lake Washington sub-watersheds.