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Green River Watershed

Green River Watershed

The Green River Watershed is the land area where rainwater drains to the Green-Duwamish River. The watershed includes Black River, Springbrook Creek, Mill Creek, Soos Creek, Jenkins and Covington Creeks, Newaukum Creek, Crisp Creek, and other tributaries. This page provides information specific to the Green-Duwamish Watershed while information spanning multiple watersheds may be found on our King County watersheds information page.

For information about the area that is a source for City of Tacoma's drinking water, please see Tacoma Public Utility's Green River Watershed page (external).

Introduction to watersheds

Basin Steward Program
Find out what Water and Land Resources' Basin Steward Program does and how to contact your Basin Stewards.

Progress in the Green-Duwamish watershed map

Green/Duwamish Watershed Strategy

Visit Our Green/Duwamish Blog (external) and learn more about the Green/Duwamish Watershed Strategy.

Notice of boating hazards

Sign up for river hazard updates:


Hazards in King County rivers
Overview of risks associated with river-related recreation and resources for water, boating and river safety.

Projects in the Green River Watershed

Water and land improvement projects, Green River Watershed
Use a map to locate projects related to flooding, wastewater treatment and stormwater in King County, Washington.

Flooding and hydrology

Green River flooding in 1995Green River flooding information
Look up real time gage data, flood phase/ river crest descriptions and learn what high water means to you along the Green-Duwamish River.

Flood photo viewer
Use a map to look up photographs of past floods on the Green River and other rivers in King County.

Hydrologic gage data map
Look up detailed gaging station data from area creeks and rivers.

Precipitation near Howard Hanson Dam, Green River (external link)
Precipitation monitoring station data, map, and graphs courtesy of the Office of the Washington State Climatologist.

Duwamish Waterway cleanup

Find pollution-related information below under Surface water and groundwater.

Duwamish Waterway superfund cleanup programs
Accomplishments to restore the Duwamish Waterway, timeline, major milestones, approaches and participants, and how to prevent future pollution.

Sediment remediation projects
Cleanup of contaminated sites in the Duwamish Waterway and Elliott Bay to enhance and restore habitat for aquatic life.

Salmon recovery

WRIA 9 salmon recovery:
Green/Duwamish River
This page provides information about the recovery of threatened salmon species in the Green/Duwamish drainage area including an overview of the planning process, scientific information, and meeting records. We welcome your participation.

Salmon recovery by subwatershed

Surface water and groundwater

Report problems: drainage and water quality 

The Restore and Protect Project
Project to identify habitat stressors and recommend restoration and protection actions to improve freshwater quality and aquatic habitat in Puget Sound streams including Soos, Cristy and Newaukum Creeks in the Green River Watershed.

Stormwater runoff pollution and how to reduce it
Tips on how to reduce water pollution from home, yard, car and pets

How can I help the Duwamish?

Green River Stormwater Retrofit Planning Project
Project to develop best practices for stormwater management, to improve local drainage techniques to meet future in-stream flow conditions and water quality goals in the Green-Duwamish River Watershed.

Green-Duwamish River watershed map
Drainage map displaying streams, lakes, drainage divides, and major roads in the area that drains to the Duwamish waterway and into Elliott Bay. The map is in Acrobat format. File size is 941 Kb.

South King County groundwater management area
Learn about plans to protect the aquifer in the south county area including the Green-Duwamish watershed localities of Renton, Kent, Auburn, Covington, Black Diamond, Maple Valley, Tukwila, and areas in between.

Benthic Macroinvertebrate Study of the Greater Lake Washington and Green-Duwamish River Watersheds Reports
This report summarizes benthic macroinvertebrate data collected from a total of 130 sites in 20 sub-basins in the Green Duwamish River and Greater Lake Washington watersheds during August and September 2003 and 2003.

Green-Duwamish River Watershed quality assessment
Comprehensive study of the Green-Duwamish River water quality and the land area draining to it, to help guide policy, prioritize cleanup and restoration efforts, and protect salmon stocks from depletion.

Green-Duwamish Microbial Source Tracking Report
This report describes the results of a microbial source tracking project on the Green River.

Stormwater runoff pollution and how to reduce it
Rainstorms rinse the watershed faster when covered by hard surfaces like roofs and roads.  Learn how stormwater brings pollution, wastes and sediments into streams, rivers and lakes and how you can keep stormwater clean.

Lake information
Lake weedwatcher project

Pollution monitoring
Ongoing water quality sampling in the Duwamish Waterway, Green River and tributary creeks. Current water quality data are available for:

Endocrine disrupting chemicals in the environment
Learn about these natural and synthetic chemicals flushed daily into our waters, and discover what King County is doing to protect public health and the environment as the science and our understanding of endocrine disruptors develops.

Wastewater treatment

South Treatment plant An overview of King County's wastewater treatment plant on the Duwamish River at 1200 Monster Road SW Renton , WA 98057. Directions

Combined Sewer Overflow Control Program
During heavy rainstorms, our combined sewers may exceed their capacity and the mixture of untreated sewage and stormwater is allowed to overflow into the Duwamish River and other water bodies to keep it from backing up into homes and businesses. Learn how King County is working to improve our system to control overflows.

Combined sewer overflow water quality assessment
Analysis of water and sediment quality in the Duwamish River and Elliott Bay to use as a basis for cleanup and restoration projects.

Recreation and appreciation

King County natural areas:

Look up individual properties protected in King County's open space system for their ecological and working resource values. The natural lands site provides addresses, pictures, location maps and rules for public use:

Interurban trail
Green River trail
The Interurban Trail is a historic rail line that runs 14 miles through Tukwila, Kent, Auburn, Algona and Pacific.  The Green River Trail runs 19 miles and provides excellent views and access to the Green River and surrounding river valley from Cecil Moses Park near Seattle to North Green River Park in Kent.

Soos Creek trail
The Soos Creek Trail features a gentle grade in a natural setting suitable for leisurely strolls, bicycle rides and horse rides.

Fishing regulations and seasons (external link)
Washington Dept. of Fish and Wildlife fishing rules for Washington State including Green/Duwamish River, its tributaries and lakes within the watershed.

Known hazards on King County rivers
Reports of confirmed logjams and obstructions that pose a hazard to recreational river users, but does not include hazards that are not known.


Aerial Photograph of Lake Meridian
Historic and recent aerial photographs
Aerial photos from the 1930's, 1970's and 1990's illustrating growth around Lake Meridian in the Soos Creek drainage, among other areas in King County.

Agriculture services and information
Comprehensive information related to agriculture in King County including parts of the Green River Watershed.

Comprehensive information related to forestry across King County including parts of the Green River Watershed.

Green-Duwamish Cooperative Weed Management Area (CWMA) Knotweed Project annual reports

Noxious weed infestation map
Interactive map showing location of regulated noxious weed infestations.

Green River Watershed facts:

  • Watershed Size: 492 square miles
  • River Length: 65 miles from Elliott Bay to Howard Hanson Dam
  • Population: Approx. 400,000
  • Salmon Species Present: Chinook, chum, coho, winter steelhead
  • Other Interesting Wildlife: Elk, black bear, cougar, bald eagle, osprey, blue heron
  • Number of Dams - two:
    • Howard Hanson Dam, Built 1962 and
    • Tacoma Water Supply Diversion Dam, Built 1911


Green-Duwamish River Watershed science documents