Lower Green River Subwatershed
Why is the Lower Green River Important to Salmon?
Lower Green Subwatershed Facts
Human population: 172,963 (2009 estimate)
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
The Lower Green River subwatershed 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 River fish going to and from the Duwamish estuary. It also provides limited rearing habitat for fish produced upstream.
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 at right shows the Lower Green River subwatershed. View a map showing this subwatershed in relation to the rest of the watershed.
Owing to its rich alluvial soils, flat topography, 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 rich 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 to the Puyallup 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.
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.
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 three reports:
- Water Quality Report 2001-2002 (published May 2004)
- Water Temperature Report 2001-2003 (published June 2004)
- Assessment of Current Water Quantity Conditions in the Green River Basin -- September 2005 (Adobe Acrobat 3.8 MB)
- Figure 1-1 - Location Map (Adobe Acrobat 1 MB)
- Figure 4-1 - Chinook Distribution Map (Adobe Acrobat 1 MB)
- Figure 4-2 - Chum, Coho, Pink, and Sockeye Distribution Map (Adobe Acrobat 1 MB)
More recent water quality data are available at the King County stream monitoring page and the Green-Duwamish Water Quality Assessment.
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.- Lower Green River Acquisition
- Habitat Inventory and Utilization Assessment of the Lower Green, Duwamish, and Nearshore Subwatersheds
- Mill Creek Mouth Restoration Planning
- Riverview Park Side Channel Restoration
Information on the status of individual projects also is tracked on the state's Lead Entity Habitat Work Schedule.
Local Governments in the Lower Green River Subwatershed
Follow the external links to learn more about these communities and what they are doing to improve habitat for salmon. |
Other Organizations/Efforts in the Lower Green River Subwatershed
King County Flood Control Zone District
The King County Flood Control Zone District maintains and operates the flood protection facilities -- levees and revetments -- on the Lower Green River. Most of its levee repair projects include fish habitat improvements.
Department of Ecology - Green River, Newaukum Creek, and Soos Creek Water Quality Improvement Project
The Washington Department of Ecology is working with local partners on a plan to address warm water temperatures and low dissolved oxygen levels in the Green River and its tributaries. This will result in the development of a Total Maximum Daily Load (TMDL).
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/Duwamish Ecosystem Restoration Project
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 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.
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
Reconnaissance Assessment Report on the Green/Duwamish and Central Puget Sound Watershed
Comprehensive information on salmon habitat as of 2000. Includes detailed information on on salmon populations, conditions in specific subwatersheds and stream basins, and maps showing salmon habitat.
Lower Green River Baseline Habitat Survey Report
Detailed information, maps, and photos of Green River mainstem habitat conditions. Also available upon request are Geographic Information System (GIS) layers with these data. Published January 2004.
Green River Watershed Page - King County
Information about the Green/Duwamish River watershed.
Environmental Information Page for WRIA 9 - Washington State Department of Ecology
Includes downloadable publications, maps, and water quality information for Green/Duwamish and Central Puget Sound Watershed (WRIA 9). Most information is related to the Green/Duwamish portion of WRIA 9.
Surf Your Watershed - U.S. Environmental Protection Agency
Site contains links to various U.S. EPA documents related to environmental conditions in the Green/Duwamish watershed. There are links for environmental parameters such as air quality and hazardous waste in addition to water quality.
Green River Hydrograph - U.S. Geological Survey
Interested in how much water is flowing in the Green River right now? This page provides current and historic data on flow for several locations on the Green River.