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

State Program Contact

 Tennessee Department of Environment and Conservation: Division of Water Resources Exit

Water Quality Standards

WQS Information
The link to Tennessee's WQS that are in effect for Clean Water Act purposes is provided. These are the WQS approved by EPA.
The state of Tennessee 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
Fish and Aquatic Life (special criteria for certain parameters identified for lakes and reservoirs, trout streams, naturally reproducing trout streams, streams in the Blue Ridge Mountains and the Mississippi Delta, Exceptional Tennessee Waters, and Outstanding National  Resource Waters).

Biological Criteria
__X__ Narrative, with regional numeric translators
_____ Numeric
_____ No criteria

Stream Use Classifications (PDF)(50 pp, 310 K)

0400-40-03-.03 Criteria for Water Uses (PDF) (46 pp, 462 K)
(m) Biological Integrity - The waters shall not be modified through the addition of pollutants or through physical alteration to the extent that the diversity and/or productivity of aquatic biota within the receiving waters are substantially decreased or, in the case of wadeable streams, substantially different from conditions in reference streams in the same ecoregion. The parameters associated with this criterion are the aquatic biota measured. These are response variables.

Interpretation of this provision for any stream which (a) has at least 80% of the upstream catchment area contained within a single bioregion and (b) is of the appropriate stream order specified for the bioregion and (c) contains the habitat (riffle or rooted bank) specified for the bioregion, may be made using protocols found in the Department’s 2017 Quality System Standard Operating Procedure for Macroinvertebrate Stream Surveys and/or other scientifically defensible methods.

Interpretation of this provision for all other wadeable streams, lakes, and reservoirs may be made using Rapid Bioassessment Protocols for Use in Wadeable Streams and Rivers (EPA 841-B-99-002) or Lake and Reservoir Bioassessment and Biocriteria (EPA 841-B-98-007), and/or other scientifically defensible methods. Interpretation of this provision for wetlands or large rivers may be made using scientifically defensible methods. Effects to biological populations will be measured by comparisons to upstream conditions or to appropriately selected reference sites in the same bioregion if upstream conditions are determined to be degraded.

Antidegradation Policy
Chapter 0400-40-03-.06 Antidegradation Statement (PDF) (46 pp, 462 K)
(a) It is the purpose of Tennessee’s standards to fully protect existing uses of all surface waters as established under the Act. Existing uses are those actually attained in the waterbody on or after November 28, 1975. Where the quality of Tennessee waters is better than the level necessary to support propagation of fish, shellfish, and wildlife, or recreation in and on the water, that quality will be maintained and protected unless the Department finds, after intergovernmental coordination and public participation, that lowering water quality is necessary to accommodate important economic or social development in the area in which the waters are located as established herein. In such waters, there shall be achieved the highest statutory and regulatory requirements for all new and existing point sources in that stream segment and sources or activities exempted from permit requirements under the Water Quality Control Act in that stream segment should utilize all cost-effective and reasonable best management practices to prevent degradation of waters. Where new or increased temperature alterations are proposed, a successful demonstration as determined by the Department under Section 316(a) of the Clean Water Act, 33 U.S.C. § 1326, shall be considered to be in compliance with this rule.

Exceptional TN waters include waters with exceptional biological diversity as evidenced by a score of 40 or 42 on the Tennessee Macroinvertebrate Index (or a score of 28 or 30 in subecoregion 73a) using protocols found in the Department’s 2017 Quality System Standard Operating Procedure for Macroinvertebrate Stream Surveys, provided that the sample is considered representative of overall stream conditions.

Biological Assessment

What biological assemblages are used in the bioassessment program?
Benthic Macroinvertebrates are primarily used, but assessments have also been based in full or in part on fish IBIs and periphyton, specifically assemblages.

Are bioassessments used to support 303(d) listings?

How are assemblages used to make impairment decisions?
Results of benthic macroinvertebrates surveys are compared to regional goals based on reference conditions.

Other uses of biocriteria or bioassessment within the water quality program:
Antidegradation, 305(b) surface water condition assessments, non-point source assessments, BMP evaluation, and restoration goals NPDES permits, trend analyses, criteria development, stressor identification, special studies and restoration goals.

Technical Support Information and Documents:

Reference condition:
Best attainable conditions for all streams with similar characteristics in a given ecological bioregion; least impacted; minimally disturbed and representative.  Characterizations: biological, chemical condition and physical habitat; minimum of three years data.

Technical reference material:
Tennessee Ecoregion Project 1994-1999 (PDF)(158 pp, 7 MB)
Revision of Tennessee's Level IV Ecoregions 2007 (PDF) (18 pp, 1 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:
Development of regionally-based numeric interpretations of Tennessee's narrative biological integrity criterion (PDF)(136 pp, 5 MB)
Standard Operating Procedure for Macroinvertebrate Stream Surveys (PDF)(266 pp, 3 MB)

Stressor identification/causal analysis approach:
Tennessee’s biological water quality criterion specifies that the alteration of biological assemblages is a “response variable’ rather than a pollutant. Additionally, the Tennessee Antidegradation provisions are significantly based on a parameter-by-parameter approach. For those reasons, biological impacts are used as a tool to help identify stressors and it is these stressors that are cited as the pollutants in the 303(d) List and Antidegradation decisions.

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