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

State Program Contact

Idaho Department of Environmental Quality Exit

Water Quality Standards

WQS Information
The link to Idaho's WQS that are in effect for Clean Water Act purposes is provided. These are the WQS approved by EPA.
The state of Idaho 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 Aquatic Life Uses

  1. Cold water (COLD): water quality appropriate for the protection and maintenance of a viable aquatic life community for cold water species. 
  2. Salmonid spawning (SS): waters which provide or could provide a habitat for active self-propagating populations of salmonid fishes. 
  3. Seasonal cold water (SC): water quality appropriate for the protection and maintenance of a viable aquatic life community of cool and cold water species, where cold water aquatic life may be absent during, or tolerant of, seasonally warm temperatures.
  4. Warm water (WARM): water quality appropriate for the protection and maintenance of a viable aquatic life community for warm water species. 
  5. Modified (MOD): water quality appropriate for an aquatic life community that is limited due to one (1) or more conditions set forth in 40 CFR 131.10(g) which preclude attainment of reference streams or conditions.

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

Water Quality Standards

Antidegradation Policy
Idaho’s antidegradation implementation procedures uses the integrated report, which relies largely on Idaho’s biological assessments, for identification of high-quality waters. In addition, Idaho’s antidegradation procedures use biological and habitat parameters to identify waters as high-quality waters even when certain numeric criteria may be exceeded - IDAPA (PDF) (190 pp, 3 MB).

Biological Assessment

What biological assemblages are used in the bioassessment program?
Benthic macroinvertebrates and fish. In addition, physical habitat is an important line of evidence on assessment.

Are bioassessments used to support 303(d) listings?
Yes. Listing methodology: Monitoring and Assessment

How are assemblages used to make impairment decisions?
Refer to detailed explanation in Water Body Assessment Guidance (PDF) (118 pp, 2 MB)

Other uses of biocriteria or bioassessment within the water quality program:
Antidegradation implementation, TMDL development and assessment, non-point source assessments, BMP evaluation, 305(b) surface water condition assessments, and restoration goals

Technical Support Information and Documents:

Reference condition:
The reference condition concept is one in which the acceptable indicator conditions are defined by the conditions observed in sites with minimal disturbance (Barbour et al. 1999, Stoddard et al. 2006). Reference sites were defined using measures of the intensity of human activity in the watersheds (such as GIS derived land use intensity), and were selected in order to have representative reference sites distributed spatially throughout Idaho. 

Technical reference material:
Biological Assessment Frameworks and Index Development for Rivers and Streams in Idaho (PDF) (229 pp, 2 MB)

Development of biocriteria 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 include standard operation procedures used in data collection, compilation, technical approaches used to develop biocriteria as well as its implementation procedures.

Technical reference material: 
Water Body Assessment Guidance (PDF) (118 pp, 2 MB)

Stressor identification/causal analysis approach:
Not applicable.

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