Corps of Engineers to Refill Lake Washington

The U.S. Army Corps of Engineers, Seattle District, will begin its annual practice of raising the level of Lake Washington Feb. 15 in preparation to meet the authorized purposes of navigation, fish passage and salinity control during the high water use in the summer months.

Boat owners and other private and commercial maritime interests along Lake Washington shores and the Lake Washington Ship Canal should expect a gradual rise to approximately 21.95 feet by early to mid-May, targeting final refill of 22 feet by June 1. Owners who maintain their vessels in a boathouse, for instance, should closely monitor the rise in lake elevations. Depending on conditions, the lake may remain at full pool (22 feet) through June and July.

Water managers plan for a 21.95-foot lake elevation by mid-May. This target is necessary to provide water for fish passage and navigation and to control the amount of saltwater entering Lake Washington.

In the spring, water use starts to increase at the locks with the operation of the smolt flumes in mid-April and increased boat traffic in May. As boat traffic increases, more water is needed to provide additional lockings. Increased lockings result in increased levels of saltwater in the ship canal, which in turn requires more water use to prevent saltwater intrusion into Lake Washington.

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