The Duwamish River in Seattle is at the end of the 93-mile long Green-Duwamish River system which drains 483 square miles from the Cascade Mountains to Elliott Bay. The lowermost 4.6 miles of the Duwamish River are located within the city of Seattle. This area is an estuary where saltwater from the sound and freshwater from the river mix. Water levels here fluctuate with the tide and amount of water in the river.
The Duwamish River is a working waterfront that supports Seattle’s port and related shipping and industrial businesses. The river is also a fishing and recreational resource. Salmon and trout entering and leaving the Green-Duwamish River use this area as a migration corridor and a large number of fish and wildlife species use the estuary for rearing.
The industrial past of the Duwamish River is still in evidence, as sediment contamination is a concern in many areas of the estuary. Water quality has improved from the past and is considered fair. However, fecal coliform bacteria concentrations frequently exceed state standard. Parts of the river also remain on Washington State’s list of impaired waterbodies for Ammonia-N and studies show an increasing trend in water temperature since the 1970’s. While the estuary continues to be a prime nursery area for Chinook salmon, there are poor shoreline habitat conditions due to overwater structures, bulkheads and little riparian vegetation like trees. Restoration activities along the banks of the river help to improve habitat.