Water Quality Improvement Project


As part of a larger effort to address all water quality impairments in the Palouse River watershed, in 2007 Ecology began a project to address high temperatures in Palouse River. This project addresses the Palouse River from the state line with Idaho to the mouth. The mouths of major tributaries are also included.

The South Fork Palouse River is a major tributary with multiple water quality problems. Please see the South Fork Palouse River Project page for more information on studies in this sub-watershed.

Why this matters

Elevated water temperature is a common problem throughout Washington. High temperatures contribute to stream habitats unable to support healthy populations of fish and other aquatic animals. Warm water affects fish’s metabolism, susceptibility to toxins and disease, reproduction, and their food supply. It can also hold less dissolved oxygen than cold water, so it makes it difficult for fish and insects that breathe through the water.

Status of the projects

The temperature study ran from May 2007-October 2007, during the time of year when the water is most likely to be impaired. Water quality modeling indicates that even under historical natural conditions the water temperature would not be likely to meet the numeric criteria during July and August. Therefore, the goal of this TMDL will be to return this river’s temperature regime to natural conditions, which will be accomplished by reestablishing “system potential shade” along the river’s stream banks. System potential vegetation consists of the plants that would naturally grow at the site as determined by climate, elevation, soil properties, and other factors.

Ecology worked with several organizations in the watershed to draft an implementation plan describing methods to address issues contributing to elevated temperatures. These issues include degraded riparian areas and wetlands, changes to natural stream hydrology, erosion, and wastewater discharges.

This plan was available for public review and comment from May 16 through June 14, 2013. Comments were reviewed and responded to in an appendix to the report. The final version of the report was revised in response to the comments and was submitted to the Environmental Protection Agency for their review and approval on July 17, 2013. EPA approved the report on November 5, 2013.

Technical information

Unless otherwise specified the following documents are Ecology publications.

Palouse Temperature Total Maximum Daily Load: Water Quality Improvement Report and Implementation Plan

Quality Assurance Project Plan: Palouse River Temperature Total Maximum Daily Load Study

Streamflow Summary for the Palouse and South Fork Palouse Rivers and Selected Tributaries, 2006-08


Related information

WRIA 34: Palouse Watershed Information (Environmental Assessment Program web site)


Back to top of page

Last updated April 2015


WRIA: #34 (Palouse)
County: Whitman

Water-body Names:
Palouse River
Cow Creek
Rebel Flat Creek
Rock Creek


# of TMDLs:
Temperature - 2

Temperature - TMDL approved by EPA, has implementation plan.

Contact Info:
Elaine Snouwaert
Phone: 509-329-3503
Email: Elaine.Snouwaert@ecy.wa.gov

Eastern Region
Department of Ecology
4601 N Monroe Street
Spokane, WA 99205-1295