Biological Water Quality Criteria

The presence, condition and numbers of types of fish, insects, algae, plants, and other organisms provide important information about the health of aquatic ecosystems. Studying these factors as a way of evaluating the health of a body of water is called biological assessment. Biological criteria are a way of describing the qualities that must be present to support a desired condition in a waterbody and serve as the standard against which assessment results are compared.

  • Technical Assistance Documents for States, Tribes and Territories
    This page contains links to general and waterbody specific guidance and technical documents for biological criteria and assessment programs.
  • Program Overview
    This page provides an overview of the Biological Criteria and Bioassessment Program through a compilation of fact sheets, memos and programmatic information.
  • Case Studies
    This page contains case studies on how bioassessment information and biological criteria have been used for a variety of water quality management activities such as development of ant-degradation policies, assessment, permitting, and enforcement.