Water Quality Improvement Projects
Snoqualmie River Basin


The Snoqualmie River watershed is an important state and community resource. Its highest points reach up to Snoqualmie Pass. From those upper reaches, the Snoqualmie flows through federal, state, and private forest lands down to Snoqualmie Falls. Below the Falls the watershed becomes an important spawning and rearing area for several salmonid species. Chinook are known to spawn heavily in the mainstem, just below the confluences of the Raging and Tolt rivers.

The watershed is also heavily used for recreation and agricultural uses. Fishing, recreational boating, swimming, and tubing are popular activities. Ranchers and crop farmers depend on clean water from the watershed to raise livestock and grow safe and healthy food. (See study area map.)

Water quality issues

Although the water quality is good in the Snoqualmie watershed in many respects, there are two areas that need improvement: bacteria and water temperature. In some tributary streams, bacteria levels are still too high. Bacteria levels in the main river have improved greatly over the last 10 years and are in pretty good shape. Water temperatures throughout the watershed are much too high during the summer. The removal of trees and other modifications to the land have made the watershed a much less hospitable place for cold-water fish to live.

Snoqualmie River, Washington State.  Photographer unknown.

Status of the projects


We prepared a report on the high water temperatures found throughout the watershed and what needs to be done to resolve the problem. The draft water quality improvement report and implementation plan was available for review and comment through June 17, 2011. After Ecology responded to the comments received and finalized the document, we submitted the TMDL to the Environmental Protection Agency (EPA) for approval on June 30, 2011. EPA approved the TMDL on August 4, 2011.



Ammonia-N, BOD (5 day), and Fecal Coliform

Ecology submitted a TMDL for ammonia-N, BOD, and fecal coliform to EPA. EPA approved it in July 1996. In March 2008, we published our updated study on fecal coliform bacteria, dissolved oxygen, ammonia-nitrogen, and pH levels in the watershed in order to determine the effectiveness of Total Maximum Daily Load (TMDL) clean-up efforts in the lower Snoqualmie River basin.

Why this matters

Ammonia (NH4+) is one measure of nitrogen, a nutrient that can increase the growth of plants and algae in water. When higher-than-normal levels of nutrients are present, plants and algae can get out of control and lead to changes in the water’s pH, dissolved oxygen and clarity. In addition, increased algae and plants can be ugly, create odor problems when they die, decompose and interfere with recreational activities like boating and swimming. In fresh waters Ammonia-N is toxic to aquatic organisms and contributes to biological oxygen demand (BOD).

Biological Oxygen Demand (BOD) is the amount of oxygen required by aerobic microorganisms (organisms that need oxygen to survive) to break down organic matter in water. It can be used to measure the amount of water pollution in a water body. High BOD values can lower dissolved oxygen levels, which are important to the health of fish and other aquatic organisms.

Fecal coliform is a type of “bacteria” common in human and animal waste. It indicates that sewage or manure is entering a water body. As the level of fecal coliform increases the risk of people getting sick from playing or working in the water increases. Bacteria can get into our waters from untreated or partially treated discharges from wastewater treatment plants, from improperly functioning septic systems, and from livestock, pets and wildlife.

People can help keep bacteria out of the water. Properly collect, bag, and trash dog poop. Check your on-site sewage system to make sure it is maintained and working properly. Ensure livestock and manure are kept away from the water.

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. Many fish need cold, clean water to survive.

One way to cool water temperature is to shade the water body by adding or retaining streamside vegetation.

Agricultural field in Snoqualmie River watershed.  Photographer unknown.

Technical information


Snoqualmie River Basin Temperature Total Maximum Daily Load: WQIR-IP

Ammonia-N, BOD (5 day), and Fecal Coliform

Snoqualmie River Basin Fecal Coliform Bacteria, Dissolved Oxygen, Ammonia-Nitrogen, and pH Total Maximum Daily Load: Water Quality Effectiveness Monitoring Report

Snoqualmie River Total Maximum Daily Load Study

Snoqualmie River, Washington State.  Photographer unknown.

Related information

Focus on Snoqualmie Watershed: Streams Too Warm

Snoqualmie Watershed Water Quality Synthesis Report: January 2009 (Salmon Conservation and Restoration)

WRIA 7: Lower Snohomish Watershed Information (Water web site)


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Last updated June 2012
  Water resource inventory area (WRIA) 7 map, Washington State.


WRIA(s): #7 (Snohomish)

Water-body Name:
Snoqualmie River watershed

Dissolved oxygen
Fecal coliform bacteria

# of TMDLs:
Ammonia-N, BOD, Fecal Coliform -16
Temperature - 17

Ammonia-N, BOD, Fecal Coliform - approved by EPA
Temperature - approved by EPA; has implementation plan

Contact Info:
Ralph Svrjcek
Phone: 425-649-7165
Email: Ralph.Svrjcek@ecy.wa.gov

Northwest Region
Department of Ecology
3190 - 160th Ave. SE
Bellevue, WA 98008-5452