Water Quality Improvement Projects (TMDLs) > WRIA 9 > Green River and Newaukum Creek Temperature Project

Water Quality Improvement Project
Green River and Newaukum Creek Area:
Temperature

Two Total Maximum Daily Load (TMDL) studies on temperature are being completed in the Lower and Middle Green River and in the Newaukum Creek watershed.

Introduction

Located in western Washington State, the Green River basin drains about 484 square miles of land area and includes portions of King County and the cities of Auburn; Black Diamond; Covington; Enumclaw; Kent; Maple Valley; Renton; Sea-Tac; and Tukwila. It flows for over 93 miles from the Cascade Mountains to Elliott Bay. (See Study Area map)

Newaukum Creek is a tributary to the Green River. Newaukum Creek runs about 14 miles from its headwaters (3,000 ft above sea level) to the confluence with the Green River near river mile 40.7 (180 ft. above sea level).

Water quality issues

Portions of the Green River and Newaukum Creek system exhibit unhealthy temperature and oxygen conditions that cause them to fail to meet Washington State water quality standards. Fish breathe oxygen in the water (dissolved oxygen). Cooler water holds more oxygen. Warmer water results in less oxygen for fish and other aquatic organisms. When water has too little oxygen or is too warm, local fish can face thermal stress and harm. These streams serve as important migration corridors and spawning and rearing areas for several salmon species, including Puget Sound Chinook; bull trout; coho; chum; pink; sockeye; kokanee; steelhead/rainbow, and cutthroat trout. These species all need cold waters for optimum health during various stages of their lives.

Status of the projects

To address the water quality issues, Ecology initiated water quality improvement ( also known as total maximum daily load, or TMDL) projects for temperature and dissolved oxygen in the Green River and Newaukum Creek. Ecology, King County, and others cooperated in a summer field study to collect data for the temperature and dissolved oxygen TMDL studies. These studies identify the pollution problems and specify how much pollution needs to be reduced to achieve clean water.

The Green River Temperature TMDL focuses on two distinct reaches of the river. The Middle Green flows from Howard Hanson Dam (river mile 54.5) downstream to “The Narrows” just east of Auburn. The Lower Green flows from The Narrows downstream to the confluence with the Black River at river mile 11. The Newaukum Creek Temperature TMDL includes the entire Newaukum Creek watershed near the city of Enumclaw.

The Green River and the Newaukum Creek Temperature TMDL reports completed a thirty-day public review process and comment period. Ecology collected and addressed the comments received from the public and agencies. After the comments are addressed and the reports were finalized, Ecology submitted the TMDLs for the Green River and Newaukum Creek to EPA on June 30, 2011.  EPA approved the Green River TMDL on August 11, 2011, and the Newaukum Creek TMDL on August 15, 2011.  The implementation plan for Newaukum Creek was included in its water quality improvement report (WQIR, consisting of the TMDL and the implementation plan).

Why this matters

Water temperature influences what types of organisms can live in a water body. Cooler water can hold more dissolved oxygen that fish and other aquatic life need to breathe. Warmer water holds less dissolved oxygen. Threatened and endangered salmon need cold, clean water to survive. One way to cool water temperature is to shade the water body by adding or retaining streamside vegetation.

Oxygen dissolved in healthy water is vital for fish and aquatic life “breathe” to survive. It is more difficult to transfer oxygen from water to blood than it is to transfer oxygen from air to blood. Therefore, it is critical that an adequate amount of oxygen is maintained in the water for this transfer to take place efficiently and sustain aquatic life. Oxygen is also necessary to help decompose organic matter in the water and bottom sediments as well as for other biological and chemical processes.

Technical information

Green River Temperature Total Maximum Daily Load: Water Quality Improvement Report (Ecology Publication)
www.ecy.wa.gov/biblio/1110046.html

Newaukum Creek Temperature Total Maximum Daily Load: Water Quality Improvement Report and Implementation Plan (Ecology Publication)
www.ecy.wa.gov/biblio/1110047.html

Quality Assurance Project Plan for the Temperature and Dissolved Oxygen TMDL in the Green River and Newaukum Creek (Ecology Publication)
www.ecy.wa.gov/biblio/0603110.html

Green River and Newaukum Creek Temperature and Dissolved Oxygen Total Maximum Daily Load Study: Data Summary Report  (Ecology Publication)
www.ecy.wa.gov/biblio/0703001.html

Related information

Focus on Green River Watershed: Water in Green River and Newaukum Creek is Too Warm (Ecology Publication)
www.ecy.wa.gov/biblio/1110043.html

Focus on temperature and dissolved oxygen in the Green River and Newaukum Creek (Ecology Publication)
www.ecy.wa.gov/biblio/0610061.html

Overview of Ecology's TMDL process
www.ecy.wa.gov/programs/wq/tmdl/overview.html

WRIA 9: Duwamish-Green Watershed Information (Environmental Assessment Program web site)
www.ecy.wa.gov/apps/watersheds/wriapages/09.html

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