Water Quality Improvement Projects (TMDLs) > Palouse Watershed Area Projects > Palouse River Mainstem

Water Quality Improvement Project
Palouse River Mainstem

Introduction

The Palouse River enters Washington State near the town of Palouse and flows west through a variety of terrain until it meets the Snake River downstream of Hooper and the Palouse Falls. When you take into account the drainage areas of all of the Palouse River tributaries, this is one of the largest watersheds in Washington. Therefore, much of Ecology’s initial water quality work has focused on the main stem Palouse River and tributaries known to be impaired. The studies described on this page are limited to the Palouse River, Rebel Flat Creek, and the mouths of several other tributaries.

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.

Water quality issues

The Palouse River is listed as impaired for dissolved oxygen, fecal coliform bacteria, temperature, pH and several historical pesticides and PCBs.

Status of the projects

Ecology began studying the pollutants for the mainstem in 2005. They broke the project into four separate studies:

• Previous studies found high levels of historical pesticides and PCBs in Palouse River fish. So, in May 2005 Ecology began the first study to examine several toxins in the Palouse River. A TMDL report detailing how the Palouse River will achieve water quality standards for PCBs and dieldrin (the only chlorinated pesticides still above standards) was completed and submitted to the Environmental Protection Agency (EPA). EPA approved the TMDL on November 9, 2007.
• Another study examined the levels and distribution of fecal coliform bacteria throughout the watershed. Fecal coliform bacteria come from the intestinal tracts of warm-blooded animals and can indicate the presence of human and animal waste which may carry disease-causing organisms. Currently the Palouse River and Rebel Flat Creek are known to be impaired by fecal coliform bacteria. This study ran from May 2007-May 2008.
  
  Note: The portion of the Palouse River, from the Idaho border to Colfax (also known as the North Fork Palouse River) was addressed under the North Fork Palouse River Bacteria TMDL.
   
• The third study examined water temperature. Temperature affects the health and distribution of fish and other aquatic life. The Palouse River is impaired by high temperatures. This study ran from May 2007-October 2007 during the time of year when the water is most likely to be impaired.
• The fourth study examined dissolved oxygen, pH, and nutrients. Data on the Palouse River and Rebel Flat Creek indicates that at times it has too little oxygen and a pH outside the range appropriate for fish and other aquatic life. The type and amount of nutrients in a waterbody can affect both oxygen and pH levels. Data for this study was collected in conjunction with the bacteria study and intensive surveys were conducted in Summer 2007. A water quality improvement report addressing temperature is in development.

To learn more about the importance of these various parameters, please see our water quality impairments page.

Other water bodies in this watershed

Cow Creek is also listed as impaired for dissolved oxygen, fecal coliform bacteria and temperature. On-going implementation activities on Cow Creek should address these water quality problems. An evaluation of these effects is underway to determine if Cow Creek can be moved from category 5 (list of impaired waters) to category 4b (addressed by a pollution control plan) on Washington's Water Quality Assessment.

Pleasant Valley Creek is listed as impaired for fecal coliform bacteria and pH. This stream is outside the scope of this project and will be addressed at a later date.

Technical information

Palouse River Dissolved Oxygen and pH Total Maximum Daily Load Study-Water Quality Study Design (Quality Assurance Project Plan)
www.ecy.wa.gov/biblio/0703110.html

Quality Assurance Project Plan: Palouse River Temperature Total Maximum Daily Load Study
www.ecy.wa.gov/biblio/0703106.html

Streamflow Summary for the Palouse and South Fork Palouse Rivers and Selected Tributaries, 2006-08
www.ecy.wa.gov/biblio/1003071.html

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