Dry conditions could cause unusually low Lake Washington lake levels

Published Aug. 2, 2023

U.S. Army Corps of Engineers officials anticipate Lake Washington’s level may drop below an elevation of 20 feet and are taking multiple steps to conserve water during this year’s dry weather.

Current projections indicate the lake could drop below an elevation of 20 feet by the end of September with water levels staying low until the fall rain returns.  With the National Weather Service 30-day forecast predicting warmer and drier conditions, lake water levels will continue to drop as long as conditions remain extremely dry.

The normal July precipitation in Seattle is 0.60 inches of rain. However, as of July 30, it only received 0.09 inches, 15 percent of normal.

USACE typically maintains the water level between 20 and 22 feet as measured officially at the Hiram M. Chittenden Locks. Corps officials keep winter water levels at 20 feet, and begin the annual summer refill in February, targeting a 22-foot elevation by late May to early June. The higher level helps meet summer water use requirements, providing water necessary for fish passage, navigation, and salinity control. Water is slowly consumed throughout the summer, until it reaches the winter level typically in early December. The early dry spring has made this year especially challenging for water management at the Locks.

The Corps is working to conserve water by maximizing lockage efficiency. By increasing the number of vessels in each locking, there are fewer lockages each day. This may create additional wait times to fill the locks, especially early in the morning or later evening when traffic is lighter. Additionally, the Corps is prioritizing using the small locks, which minimizes water used in the large locks resulting in significant water conservation.

Applying these conservation measures will help reduce the risk for needing additional measures later in the summer. However, as lake levels change, additional measures to conserve water could be carried out.

USACE officials are recommending floating homeowners, others with floating structures and vessels moored on Lakes Washington and Union, and along the Lake Washington Ship Canal, to prepare for possible lower water levels.

The record low lake level is 18.35 feet, reached in 1958. The lowest recent recorded water level below 20 feet was 19.91 feet, measured in August 2015.

For more information about Locks activities visit www.facebook.com/ChittendenLocks or www.twitter.com/ChittendenLocks

Nicole L. Celestine

Release no. 23-022