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Lower Green River Subwatershed
Green/Duwamish and Central Puget Sound Watershed
Water Resource Inventory Area (WRIA) 9
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Why is the Lower Green Subwatershed Important to Salmon?
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The Lower Green River subwater-shed has been dramatically transformed over the last 130 years but still performs a vital role for the salmon of the watershed. The Lower Green is the vital migration corridor used by Middle Green fish going to and from the Duwamish estuary. It also provides limited rearing habitat for fish produced upstream.
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Subwatershed Salmon Habitat Overview
This subwatershed starts at River Mile 11, the upper limit of the Duwamish estuary, and winds 32 river miles south and east to the Highway 18 bridge. Its major tributaries include Mill Creek (Auburn) and Mill/Springbrook Creek (Renton and Kent).
The map below shows the Lower Green River subwatershed. Click here for a map showing this subwatershed in relation to the rest of the watershed.
Owing to its rich alluvial soils, flat lands, and easy access to first river and later railroad and road transportation, this part of the watershed has undergone multiple transformations since 1870. After being cleared of forests, it became bountiful agricultural land. Following World War II, the Kent Valley became a center for manufacturing, warehousing, and commerce.
Accompanying these land use changes were a variety of other habitat modifications. The White River was diverted in 1906, resulting in a decrease in water flow and sediment and a lowering of the floodplain. Upstream activities in the Middle Green -- Howard Hanson Dam operations and water withdrawal at the Tacoma Headworks -- have led to an unnatural flow regime in which flood flows were reduced and summer flows were lower. Other significant habitat alterations have been the construction of a series of levees along most of the length of the Green River mainstem in this subwatershed. These levees cut off salmon access to side-channel habitats such as sloughs and adjacent wetlands where young salmon fed and took shelter.
Currently this reach is utilized for the upstream and downstream migration and rearing for all native salmon species. It has limited spawning
habitat for Chinook, pink, sockeye, chum, and steelhead.
Lower Green Subwatershed Facts
Human population: 154,000 (1999)
Primary land uses: residential (50%),
industrial (17%), commercial (10%)
Mean annual discharge:
over 2,000 cubic feet per second
Salmon species currently present:
Chinook, coho, chum, pink, sockeye, steelhead, coastal cutthroat trout
Additional salmon species thought to be here historically: bull trout
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Where the Fish Are in the Lower Green River Subwatershed
Fish distribution maps show where anadromous salmon and trout have been found or should be present.
Problems on the Mainstem Green River
- Urbanization, water diversions, and revetments that are:
- Lowering the floodplain and disconnecting off-channel habitats such as sloughs and adjacent wetlands;
- Reducing large woody debris and associated instream complexity, such as pools and riffles;
- Creating some adult salmon migration problems due to low flows;
- Causing chronic water quality problems; and
- Severely reducing streamside ("riparian") habitats and associated functions such as shade and insect input.
Problems on Tributary Streams 
- Intense urbanization and infrastructure (roads, public facilities) that are:
- Reducing forest cover and increasing impervious surfaces leading to hydrologic disruptions to stream flow, channel degradation, increased sedimentation, and decreased water quality;
- Channelizing streams to facilitate land use practices;
- Creating barriers to fish passage; and
- Introducing non-native plant and animal species.
Recent Habitat Information
Additional information on the quality of habitat along Green River mainstem in this subwatershed is detailed in the Lower Green River Baseline Habitat Survey Report published in January 2004.
Habitat historically found in the Lower Green River Subwatershed (Adobe Acrobat 1.5 MB) has been researched to inform decisions about future restoration.
Water quality information on this stretch of the Green River is available in two reports:
More recent water quality data are available at the King County Water Quality Data page.
See also water quality data from the Washington State Department of Ecology.
Project Solutions to These Problems
Projects funded by the Salmon Recovery Funding Board and other grantors are listed here. The projects listed below are only a few of the various projects of governments and volunteer groups in this subwatershed.
Other planned projects in this subwatershed can be located using the WRIA 9 Interactive Work Schedule and Project Portfolio.
Local Governments in the Lower Green River Subwatershed
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Follow the external links to learn more about these communities and what they are doing to improve habitat for salmon.
* Indicates that volunteer opportunities or other specific salmon related information are available on this site.
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Other Organizations/Efforts in the Lower Green River Subwatershed
- Green-Duwamish Ecosystem Restoration Project Page of the U.S. Army Corps of Engineers
The US Army Corps of Engineers, in partnership with King County, the cities of the watershed, the Muckleshoot and Suquamish Tribes, state agencies, and local interests have developed the Green/Duwamish Ecosystem Restoration Project to restore the ecosystem of the watershed. Several projects are in the Lower Green River subwatershed.
- Green River Flood Control Zone District
The Green River Flood Control Zone District is a quasi municipal corporation whose boundaries encompass the Lower Green River subwatershed from Auburn to Tukwila (in other words, nearly all of the Lower Green River subwatershed). The District is primarily responsible for maintaining and operating important flood protection facilities on the Lower Green River. In recent years, it has included fish habitat improvements into its levee reconstruction projects.
- King County Basin Stewards
The King County Water and Land Resources Division has Basin Stewards for specific basins. These stewards:
- Respond to citizen inquiries concerning issues in their part of the watershed
- Coordinate efforts among various public agencies
- Facilitate watershed improvement projects
- Provide assistance to monitoring programs
- Provide public education opportunities
The basin steward for the Lower Green River subwatershed is Josh Kahan, 206-296-8052.
- King Conservation District
Since 1949, the KCD has been helping the people of King County manage their natural resources by educating landowners, schools groups, scientists, consultants and agencies in recognizing problem situations and avoiding the creation of them. KCD also provides technical assistance in solving problems.
- Green River Natural Resources Area - City of Kent
The Green River Natural Resources project transformed an abandoned sewage lagoon system into a combined stormwater detention and enhanced wetland facility that provides a rich diversity of wildlife habitat. This 304-acre City of Kent park is one of the last remaining open tracts of land in the lower Green River valley and incorporates state-of-the-art techniques of wetland creation and enhancement, urban wildlife management, and stormwater treatment. It contributes clean water and aquatic habitat at the headwaters of Mill/Springbrook Creek in Kent and Renton.
- Black River Watershed Alliance
The Alliance cares for the Black River watershed and its wildlife by taking students on field trips to the Black River, involving members of the community in monitoring the health of the Black River, and supporting restoration of native vegetation.
- Friends of the Green River
This group focuses on protection and water conservation in the Green River watershed, including the Middle Green.
- Green-Duwamish Watershed Alliance
The Alliance is dedicated to the protection and restoration of the Green/Duwamish Watershed through partnerships with communities, tribes, businesses, and government agencies.
- Star Lake Community Club
The club focuses on issues affecting Star Lake.
- Rainier Audubon
The mission of the Rainier Audubon is to conserve and restore natural ecosystems and protect birds and other wildlife for the benefit of humanity and biological diversity in South King County.
- South King County Group, Cascade Chapter of the Sierra Club
The Sierra Club works on a variety of environmental issues including water quantity, water quality, and habitat for salmon and other aquatic creatures.
Information Resources for the Lower Green River Subwatershed
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