Upper Green River Subwatershed Green/Duwamish and Central Puget Sound Watershed Water Resource Inventory Area (WRIA) 9

Why is the Upper Green Subwatershed Important to Salmon?

Although salmon do not currently have access to the Upper Green River subwatershed due to two dams downstream, this part of the watershed has some good habitat. Scientists think that if we can help the fish upstream and downstream past these dams -- which should be possible on a test basis by 2009 -- they will be able re-establish themselves in the Green River mainstem and major tributaries in this subwatershed.

Subwatershed Salmon Habitat Overview

The Upper Green River Subwatershed begins at River Mile 64.5, the location of modern-day Howard Hanson Dam and stretches 30 miles east the Cascade Crest. This subwatershed is home to the headwaters of the Green/Duwamish River.

The map below shows the Upper Green River subwatershed. Click here for a map showing this subwatershed in relation to the rest of the watershed.

Prior to 150 years ago, this part of the watershed was probably home to Chinook, coho, and steelhead salmon.

Since 1911, salmon access to this part of the watershed has been blocked by a water diversion dam at River Mile 61. The City of Tacoma constructed this dam to provide drinking water. While Tacoma has limited public access in a portion of this subwatershed to protect the drinking water supply, commercial timber harvest has occurred throughout this portion of the watershed.

This activity has altered many of the ecological processes and degraded much of the habitat. Roads and a railroad also have had an impact on the mainstem as described below. Currently, only the resident form of coastal cutthroat and some anadromous salmonids that have been transported around the dams (juvenile steelhead trout, Chinook and coho salmon, and adult winter steelhead trout) use this portion of the watershed.

In 1962, Howard Hanson Dam (HHD), a flood control dam, was completed at River Mile 64.5, which is the downstream boundary of this sub-watershed. HHD also currently is a complete barrier to upstream and downstream adult migration. The large flood control dam and associated reservoir interrupts the natural flow of sediments and large woody debris to lower mainstem Green River reaches. It also chronically floods upstream habitat when the reservoir is full.

The Army Corps of Engineers and the City of Tacoma are working together to construct and operate fish passage facilities to make possible the safe migration of fish upstream and downstream past the two dams. Construction of the upstream fish passage facility by Tacoma Public Utilities was completed in 2005. Construction of the downstream fish passage facility by the Army Corps of Engineers should be complete by 2009.

Where the Fish Are in the Upper 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

While the two dams currently block upstream fish passage and Howard Hanson Dam severely hampers downstream passage, some salmon do reside in this reach and are affected by existing habitat conditions. When fish passage past the dams is improved in the future, existing habitat conditions will affect salmon that are reintroduced to the area. These problems include:

• The placement of roads and railroads immediately adjacent to rivers and streams resulting in:
  
  • Reduction and degradation of riparian habitat functions such as shade and large woody debris; and
    
  • Limited lateral channel migration and the creation of new habitat.
    
• A reservoir pool that is:
  
  • Reducing spawning habitat and riparian functions due to periodic flooding of 4.5 miles of the Green River mainstem and 3.0 miles of tributaries; and
    
  • Delaying juvenile outmigration.

Problems on Tributary Streams

• Logging practices resulting in:
  
  • Reduced streamside ("riparian") habitat functions such as shade and instream large woody debris;
    
  • Fish passage barriers;
    
  • Excessive sedimentation, especially of fine sediments;
    
  • Decreased water quality; and
    
  • Altered stream hydrology.
    

Recent Habitat Information

Additional information on the quality of habitat -- historical and current -- along Green River mainstem in this subwatershed is detailed in the Upper Green River Historical and Current Habitat Conditions Report (Adobe Acrobat 16 MB) published in June 2004.

Water quality information on this stretch of the Green River is available in the Water Temperature Report 2001-2003 (published June 2004).

Project Solutions to These Problems

Local Governments in the Upper Green River Subwatershed

Other Organizations/Efforts in the Upper 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 Upper Green River subwatershed.
• Howard Hanson Dam Additional Water Storage Project
  This Army Corps of Engineers project includes raising the pool level of Howard Hanson Reservoir, constructing a fish passage facility for downstream salmon migration, and operation of the dam to provide more water for human water supply and instream flow for salmon. Also included are downstream habitat improvements consisting of introduction of spawning gravel and large woody debris into the river.
• Howard Hanson Dam
  Information on the Howard Hanson Dam, constructed in 1962 and operated by the U.S. Army Corps of Engineers for flood protection purposes.
• Tacoma Water Operations on the Green River (Tacoma Public Utilities)
  Tacoma Water serves more than 83,000 customers in the cities of Tacoma and University Place, plus portions of Puyallup and Pierce and South King counties. The majority of this water is taken from the Green River. Tacoma operates the diversion dam ("Headworks") at River Mile 61, which is located just below the Upper Green River subwatershed. Tacoma restricts access to the western part of the Upper Green River subwatershed to protect its water supply.
• Friends of the Green River
  This group focuses on protection and water conservation in the Green River watershed, including the Upper Green.

Information Resources for the Upper 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.
• WRIA 9 Project Portfolio Database
  Use an interactive database to identify projects in this part of the watershed.
• Green River Watershed Page - King County
  Information about the Green/Duwamish River watershed.
• Green River Water Supply
  Information from Tacoma Public Utilities on water supply and water use.
• 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.