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

State Program Contact

Colorado Department of Public Health and Environment Exit

Water Quality Standards

WQS Information
The link to Colorado's WQS that are in effect for Clean Water Act purposes is provided. These are the WQS approved by EPA.
The state of Colorado 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
Multiple designated use categories. Multiple thresholds for MMIs and auxiliary metrics by Biotype.

  • Class I or II
  • Cold or Warm

Biological Criteria
__X__ Narrative, with a biocriteria policy adopted into rule that includes quantitative implementation procedures or translators
_____ Numeric
_____ No criteria

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

Biological Assessment

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

Are bioassessments used to support 303(d) listings?
Yes. Listing Methodology: Section 303(d) Listing Methodology

How are assemblages used to make impairment decisions?
Assessment of Benthos support 303(d) listing decisions of the aquatic life use. Assessment of Periphyton chlorophyll-a support 303(d) listing decisions for the recreation use.

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

Technical Support Information and Documents:

Reference condition:
The Commission continues to support the use of “reference condition” or “expected condition” as the basis for characterizing use support. It is important to note that this concept of use support embraces considerable variation in the biological community.

Technical reference material:
Methodology to Determine Use Attainment for Rivers and Streams Policy Statement 10-1 (PDF)(167 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 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:
Methodology to Determine Use Attainment for Rivers and Streams Policy Statement 10-1 (PDF) (167 pp, 2 MB)

Stressor identification/causal analysis approach:
Stressor ID has really been low key in the Watershed Section at WQCD – the only output of these efforts was the development of Tolerance Indicator Values or TIVs for the revised Sediment Guidance (Policy 98-1) in 2014. Resources have not been adequately dedicated to Stressor ID.

Technical reference material:
Guidance for Implementation of Colorado's Narrative Sediment Standard (PDF) (93 pp, 2 MB)

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