Updates to the Lake Washington Ship Canal and Ballard Locks model, Seattle, Washington, 2016–20
The Hiram M. Chittenden Locks (Ballard Locks or Locks) and Lake Washington Ship Canal connect freshwater Lake Washington with saline Shilshole Bay of Puget Sound. The Locks are operated by the U.S. Army Corps of Engineers (USACE) and serve commercial and recreational vessels. Anadromous salmonids migrate through the canal by making use of a fish ladder at the Locks. To help understand canal hydrodynamics, water temperature, and salinity, a two-dimensional model (CE-QUAL-W2) of the Locks and Lake Washington Ship Canal was constructed by WEST Consultants, Inc. In cooperation with USACE, the U.S. Geological Survey reviewed and updated this model and documentation. The review, published previously, recognized the strengths of the model and suggested some modifications and updates. This report documents these modifications, reports on sensitivity testing, describes model recalibration, and reports model results for calendar years 2016–20. Modeled water velocity was less than 0.2 meter per second at most sites and depths; velocity was greater nearer the Locks. Water age, which estimates residence time, was greatest during September and October. Water temperature was greater near-surface and cooler near the channel bottom at some times and locations. The model also simulated the inflow of lower-salinity waters from Lake Washington and the import of higher-salinity waters from the Locks.