The Hiram M. Chittenden Locks are a complex of locks that provide a link for boats between the saltwater of the Puget Sound and the fresh water of the Ship Canal connecting to Lake Union and Lake Washington. To the area locals, they are commonly known as the Ballard Locks. The Locks, link salty Puget Sound with the fresh waters of Salmon Bay, Lake Union, Portage Bay and Lake Washington.
The Locks serve three significant purposes. First of all, to move boats from the water level of the lakes to the water level of Puget Sound, and vice versa. Then, to prevent the mixing of seawater from the Sound with the fresh water of the lakes (also known as saltwater intrusion). Finally, to maintain the fresh water level of Lake Washington and Lake Union at approximately twenty feet above sea level.
The complex includes two locks, a small (30 x 150 ft, 8.5 x 45.7 meters) and a large (80 x 825, 24.4 x 251.5 meters). The complex also includes a (235-foot, 71.6 meters) spillway with six (32 x 12-foot) gates to assist in water-level control. A fish ladder is created in the locks for the migration of fish, primarily salmon. The nearby grounds feature a visitor's center and the Carl S. English, Jr. Botanical Gardens.
Both tourists and locals enjoy watching the parade of sailboats, motorboats, tugs, barges and yachts passing through the Locks. Visitors travel from all over the state to pass a sunny day watching boats of all shapes and sizes arrive into the locks. Upon arrival the water level is adjusted to allow their safe passage to the lake or Sound.
The fish ladder was built to allow salmon to pass between fresh and salt water. Glass panels make it possible to view the fish as they navigate their way through the ladder, adjusting to different levels of salt each step of the way. Occasionally, a clever sea lion will hang out, waiting for his next meal. Although the viewing area is open year-round, the "peak" viewing time is during spawning season, from about the beginning of July through mid-August. The fish approaching the ladder smell the attraction water, recognizing the scent of Lake Washington and its tributaries. The salmon enter the ladder, and either jump over each of the 21 weirs or swim though tunnel-like openings. They exit the ladder into the fresh water of Salmon Bay. They continue following the waterway to the lake, river, or stream where they were born. Once there, the females lay eggs, which the males fertilize. Most salmon die shortly after spawning.
There is also a public art work, commissioned by the Seattle Arts Commission that provides literary interpretation of the experience through recordings of Seattle poet Judith Roche's "Salmon Suite," a sequence of five poems tied to the annual migratory sequence of the fish.