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

State Program Contact

Arizona Department of Environmental Quality Exit

Water Quality Standards

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

You may need a PDF reader to view some of the files on this page. Refer to EPA’s about PDF page to learn more.

Designated Aquatic Life Uses
Arizona has adopted narrative and numeric biocriteria to protect aquatic life uses in wadeable, perennial streams designated for either coldwater aquatic and wildlife (A&Wc) or warmwater aquatic and wildlife (A&Ww). Those biocriteria allow the state to define expected conditions relative to reference streams which have been characterized as least disturbed conditions.

  • A & W warm
  • A & W cold
  • A & W effluent dependent
  • A & W ephemeral

Biological Criteria
__X__ Narrative statement
__X__ Numeric
_____ No criteria

Arizona Administrative Code R18-11-108(E)
R18-11-108.01 Narrative Biological Criteria (PDF)(77 pp, 794 K)

A wadeable, perennial stream shall support and maintain a community of organisms having a taxa richness, species composition, tolerance, and functional organization comparable to that of a stream with reference conditions in Arizona.

  1. The narrative biological criteria in this Section apply to a wadeable, perennial stream with either an aquatic and wildlife (cold water) or an aquatic and wildlife (warm water) designated use.
  2. The biological standard in is met when a bioassessment result, as measured by the Arizona Index of Biological Integrity (IBI), for cold or warm water is:
    1. Greater than or equal to the 25th percentile of reference condition, or
    2. Greater than the 10th percentile of reference condition and less than the 25th percentile of reference condition and a verification bioassessment result is greater than or equal to the 25th percentile of reference condition.
  3. Arizona Index of Biological Integrity (IBI) scores
    1. Bioassessment Result
      1. Greater than or equal to the 25th percentile of reference condition
        1. A&Wc Index of Biological Integrity Scores ≥ 52
        2. A&Ww Index of Biological Integrity Scores ≥ 50
      2. Greater than the 10th and less than the 25th percentile of reference condition
        1. A&Wc Index of Biological Integrity Scores = 46 - 51
        2.  A&Wc Index of Biological Integrity Scores = 40 - 49

Antidegradation Policy
Antidegradation (PDF) criteria in WQS (R18-11-107.01) does not currently include a bioassessment methodology(132 pp, 3 MB)
Implementation procedures for Antidegradation (PDF)(94 pp, 937 K)

Biological Assessment

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

Are bioassessments used to support 303(d) listings?
No. Listing Methodology: ADEQ needs to have the 303d listing criteria included in the Impaired Waters Identification Rule (IWIR) prior to listing streams with impaired IBI Score. The Rules moratorium in AZ is preventing this.

How are assemblages used to make impairment decisions?
AZDEQ cannot yet make impairment decisions based on macroinvertebrate bioassessments. When the IWIR is updated, bioassessments can then be used to list impaired streams. AZDEQ has two multimetric IBIs for warm and coldwater stream macroinvertebrate communities and is developing a periphyton (diatom) bioassessment tool. It’s anticipated that the two assemblage indexes will be applied independently.

Other uses of biocriteria or bioassessment within the water quality program:
305(b) surface water condition assessments

Technical Support Information and Documents:

Reference condition:
AZDEQ’s biocriteria establish biological thresholds that protect the naturally occurring benthic macroinvertebrate communities expected in coldwater and warmwater perennial streams. The two designated uses apply according to elevation differences with the coldwater use applying to waters generally above 5,000 feet, and warmwater use applicable to those waters below 5,000 feet. The reference condition represents least disturbed conditions. In Arizona, regional reference conditions have been developed statewide for bioassessment purposes; with 30-50 reference sites each for warm and cold water stream types. All the following conditions must be met for a stream reach to be considered reference. These are minimum criteria which must be met.

  • No known discharges upstream
  • No major impoundments upstream
  • No channel alterations at the site
  • Located >0.5 km downstream of road crossings
  • Site should be free of local land use impacts
  • Site should be truly perennial (presence of fish, univoltine insects, riparian indicators)
  • No violations of pH or dissolved oxygen water quality standards
  • ADEQ Habitat score > 14
  • Accessible (within a 2-hour hike or 3-4 mi from nearest road)

Approximately 10 Reference streams are monitored each year and a re-evaluation of their condition is done periodically to update the database of reference sites and update the IBI threshold scores.

Technical reference material:
ADEQ. 2007. Technical support documentation for the narrative biocriteria standard. Arizona Department of Environmental Quality, Phoenix, AZ.
ADEQ. 2015. Surface Water Section Quality assurance program plan. 2015. Arizona Department of Environmental Quality, Phoenix, AZ.
ADEQ. 2015. Standard operating procedures for Surface Water Quality Sampling. 2015. Arizona Department of Environmental Quality, Phoenix, AZ.

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:
Implementation Procedures for the Narrative Biocriteria Standard (PDF)(18 pp, 350 K)

Stressor identification/causal analysis approach:
Not applicable.

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