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Bioassessment and Biocriteria Program Status for Washington: Streams and Wadeable Rivers

State Program Contact

Washington Department of Ecology Exit

Water Quality Standards

WQS Information
The link to Washington's WQS that are in effect for Clean Water Act purposes is provided. These are the WQS approved by EPA.
The state of Washington provided information and links to sections of their administrative code on designated aquatic life use, biological criteria, antidegradation as well as technical support documents and information on its bioassessment and biocriteria programs. These are included for your convenience and may or may not reflect the most recently EPA approved WQS. The following links exit the site Exit

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Designated Freshwater Aquatic Life Uses
  • Char spawning and rearing
  • Core summer salmonid habitat
  • Salmonid spawning, rearing, and migration
  • Salmonid rearing and migration only
  • Non-anadromous interior redband trout (no waterbodies currently assigned)
  • Indigenous warm water species (no waterbodies currently assigned)

Biological Criteria
__X__ Narrative, with quantitative implementation procedures or translators
_____ Numeric
_____ No criteria

WAC 173-201A-200 (1) It is required that all indigenous fish and nonfish aquatic species be protected in waters of the state in addition to the key species described [in the aquatic life use categories]

Antidegradation Policy
Use of biocriteria or bioassessment not included in antidegradation policy.

Biological Assessment

What biological assemblages are used in the bioassessment program?
Benthic macroinvertebrates, fish, amphibians, and periphyton

Are bioassessments used to support 303(d) listings?
Yes. Listing methodology: Assessment of Water Quality for the Clean Water Act Section 303(d) and 305(b) Integrated Report

How are assemblages used to make impairment decisions?
Benthic macroinvertebrates are currently the only biological assemblage used for 303d listing.

Other uses of biocriteria or bioassessment within the water quality program:
TMDL development and effectiveness monitoring, non-point source assessments, BMP evaluation, stressor identification analysis, 305(b) surface water condition assessments, and restoration goals

Technical Support Information and Documents:

Reference condition:
Ecology currently has over 100 reference sites that are monitored throughout the state, with new sites added regularly. Some sites are monitored annually, while others are sampled on a rotating basis.

Technical reference material:
Stream Biological Monitoring

Development of bioassessment thresholds involves the collection and interpretation of biological data – e.g. benthic macroinvertebrates, fish, and periphyton. During this process entities typically use biological metrics (usually aggregated into a multimetric index) and/or multivariate analysis to assess whether a waterbody is meeting its designated aquatic life use(s). The reference materials included below include standard operation procedures used in data collection, compilation, technical approaches used to develop biocriteria as well as its implementation procedures.

Technical reference material:
Stream Biological Monitoring Methods

Stressor identification/causal analysis approach:
Linked stressor identification and causal analysis

Technical reference material: 
Guidance for Stressor Identification of Biologically Impaired Aquatic Resources in Washington State

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