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

State Program Contact

Minnesota Pollution Control Agency Water Exit

Water Quality Standards

WQS Information
The link to Minnesota's WQS that are in effect for Clean Water Act purposes is provided. These are the WQS approved by EPA.
The state of Minnesota 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
Designated use class framework includes seven use classes which protect uses including drinking water, aquatic life, recreation, agriculture, wildlife, and industry. Aquatic life uses protect fish and associated aquatic life. Aquatic life uses are further classified by water body type including cold water lakes and streams, warm water lakes and streams, and wetlands.

Aquatic life and recreation, Class 2.34 subclasses:

  • 2A cold water streams and lakes
  • 2B cool & warm water fishery
  • 2D wetlands

Biological Criteria
__X__ Narrative statement
__X__ Numeric
_____ No criteria

7050.0150 Determination of Water Quality, Biological and Physical Conditions, and Compliance with Standards. Subp. 3. Narrative standards.
For all class 2 waters, the aquatic habitat, which includes the waters of the state and stream bed, shall not be degraded in any material manner, there shall be no material increase in undesirable slime growths or aquatic plants, including algae, nor shall there be any significant increase in harmful pesticide or other residues in the waters, sediments, and aquatic flora and fauna; the normal aquatic biota and the use thereof shall not be seriously impaired or endangered, the species composition shall not be altered materially, and the propagation or migration of aquatic biota normally present shall not be prevented or hindered by the discharge of any sewage, industrial waste, or other wastes to the waters.

Antidegradation Policy
Use of biocriteria or bioassessment not included in antidegradation policy (Parts 7050.0265 and 7050.0270)

Biological Assessment

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

Are bioassessments used to support 303(d) listings?
Yes. Listing Methodology: Minnesota's Impaired Waters List

How are assemblages used to make impairment decisions?
Independently applied

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

Technical Support Information and Documents:

Reference condition:
Reference sites are defined as least/minimally disturbed reaches/areas within a specific geographic region, within a given aquatic classification framework. The criteria used to define reference sites are based on land use and habitat and are adjusted by region (basin, ecoregion, etc.). Candidate reference sites are initially selected using GIS coverages including land use, point sources, ditching, and feedlots.

Biological Condition Gradient (BCG) was integral to the development of biocriteria in Minnesota streams. Using populations of reference sites, BCG levels consistent with attainment of aquatic life use goals were determined for three tiered aquatic life uses (TALUs): Exceptional, General, and Modified uses. This BCG threshold was used to calculate IBI scores consistent with biological assemblages meeting goals. The use of the BCG was especially important for regions of Minnesota where few reference sites were extant and limited the use  of an approach that relied solely on the reference condition to establish goals. The result is a statewide biocriteria framework for different stream habitat types which have a consistent goal regardless of existing biological condition. Stream biocriteria are implemented as numeric criteria which are adopted in rule. Lake biocriteria were developed using a similar methodology although lake biocriteria are implemented as numeric translators of narrative standards. 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.

Minnesota uses multimetric indices called indices of biological integrity (IBI) to measure the condition of aquatic life. Biological assemblages are sampled (e.g., fish and macroinvertebrates in streams) and are scored using multimetric models specific to the habitat type (e.g. southern large river, northern cold water stream). Scores are compared against biocriteria to determine if the habitat is meeting beneficial use goals specific to that habitat type.

Technical reference material:
Index of Biological Integrity
MPCA Water Rules

Stressor identification/causal analysis approach:
Stressor identification

Technical reference material: 
Biological Monitoring of Water in Minnesota

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