Water Quality Improvement Projects (TMDLs) > Wenatchee River Basin Area Projects > Wenatchee River Area Temperature Project

Water Quality Improvement Project
Wenatchee River Area:
Temperature

Water quality issues

The temperature of a stream reflects the amount of heat energy in the water. Changes in water temperature within a particular segment of a stream are induced by the balance of heat exchange between the water and the surrounding environment during transport through the segment. The temperature of a stream is vitally important when it comes to aquatic life, fish spawning and rearing, and other beneficial uses.

The Wenatchee River and some of its tributaries (Chiwaukum Creek, Icicle Creek, Little Wenatchee River, Nason Creek, Mission Creek, and Peshastin Creek) are included on Washington State’s list of water-quality-impaired waters because of high temperatures.

Many processes that we cannot control increase temperature, but there are also many that we can control. The following processes affect water temperatures in the Wenatchee National Forest:

• Decreasing riparian vegetation height, width, and /or density reduces stream surface shading, which increases the amount of solar radiation reaching the stream surface.
• Activities such as livestock grazing, recreation, agriculture, and logging contribute to reduced riparian shade.
• Channel widening (increased width-to-depth ratios) increases the stream surface area exposed to solar radiation.
• In-stream withdrawals and hydraulically-connected groundwater withdrawals may reduce summertime base flows. Reducing the amount of water in a stream can increase stream temperature.

Why this matters

Water temperature influences what types of organisms can live in a waterbody. 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.

Decreased water temperatures can be met by restoring riparian vegetation, increasing instream flow by improving irrigation techniques, and decreasing the amount of suspended sediment in the water by using bank stabilization best management practices (BMPs).

Status of the project

The TMDL technical analysis for Water Temperature in the Wenatchee National Forest was completed in November 2003.  The Wenatchee River Watershed Temperature Total Maximum Daily Load - WQ Improvement Report was completed in July 2007.  EPA approved the WQIR in August 2007. Additionally, the TMDL works collaboratively with the Wenatchee Forest TMDL and the Wenatchee Watershed Plan to address temperature impairments holistically for the entire Wenatchee River watershed.

Technical information

Wenatchee River Temperature Total Maximum Daily Load Study (Ecology Publication)
www.ecy.wa.gov/biblio/0503011.html

Quality Assurance Project Plan: Wenatchee River Temperature, Dissolved Oxygen, and pH Total Maximum Daily Load, Year 1 Technical Study (Ecology Publication)
www.ecy.wa.gov/biblio/0203069.html

Quality Assurance Project Plan: Wenatchee River Temperature, Dissolved Oxygen, pH, and Fecal Coliform Total Maximum Daily Load Year 2 Technical Study (Ecology Publication)
www.ecy.wa.gov/biblio/0303106.html

Wenatchee River Watershed Temperature Total Maximum Daily Load - WQ Improvement Report
www.ecy.wa.gov/biblio/0710045.html

Wenatchee National Forest Water Temperature Total Maximum Daily Load: Technical Report (Ecology Publication)
www.ecy.wa.gov/biblio/0310063.html

Related information

Water Cleanup Plans: Taking the temperature of the Wenatchee watershed (Ecology Publication)
www.ecy.wa.gov/biblio/0210028.html

WRIA 45: Wenatchee Watershed Information (Environmental Assessment Program web site)
www.ecy.wa.gov/apps/watersheds/wriapages/45.html

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