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Reference Condition Concept
The Clean Water Act (CWA) poses significant challenges to states and tribes charged with evaluating whether aquatic resources under their management achieve the biological integrity objective and the “protection and propagation” goals. One of the critical challenges is the development of a standard or benchmark by which to judge whether particular water bodies are in accordance with the CWA objective and goals. The concept of a reference condition and its implementation form the foundation on which to make such judgments (Stoddard et al. 2006a).
Reference conditions have been applied at site-specific and regional scales. Regional reference condition, described here, is recommended to support biological criteria. Biological criteria are used to detect deviation from reference condition to determine whether water bodies meet their water quality standards. The Biological Condition Gradient (BCG) is a scientific narrative model for interpreting biological response to increasing effects of stress on aquatic ecosystems. The BCG describes how attributes of aquatic ecosystems change in response to increasing levels of human disturbance (Davies and Jackson 2006).
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The Biological Condition Gradient (BCG) is a tool for developing more precise aquatic life uses. The BCG displays six positions of biological condition along a stressor-response curve, with Position 1 exhibiting the least stress and highest quality condition, and Position 6 representing the greatest stress and lowest quality. (Modified from EPA 2005)
Material above taken from Best Practices for Identifying Reference Condition in Mid-Atlantic Streams.
Learn more about reference condition by reading:
- Best Practices for Identifying Reference Condition in Mid-Atlantic Streams (EPA-260-F-06-002, August 2006) (8pp, 1.49MB About PDF)
- Reference site criteria (from Key Concepts)
- Reference condition (from Key Concepts)
- Reference condition concept (from Best Practices)
- Reference condition types (from Best Practices)
- Reference condition benchmarks (from Best Practices)
- Approaches to Deriving Reference Conditions (from Best Practices)
- Reference sites did not always meet criteria for reference condition in Developing Biological Indicators: Lessons Learned from Mid-Atlantic Streams
- Regional Reference Concept (from Monitoring Web site)
- Great Rivers Reference Condition Workshop (from Biocriteria Web site)
- Aquatic Life Use Support - Reference Condition (from Biocriteria Web site)
- Basic Reference Condition and Classification Techniques (from Biocriteria Web site)
- Reference Condition Case Studies (from Biocriteria Web site)
- Advanced
Reference Condition Techniques, Special Circumstances and Problem Solving (from Biocriteria Web site)
Citations:
Davies, S.P. and S.K. Jackson. 2006. The biological condition gradient: a descriptive model for interpreting change in aquatic ecosystems. Ecological Applications 16(4):1251-1266
Stoddard, J.L., D.P. Larsen, C.P. Hawkins, R.K. Johnson and R.H. Norris. 2006a. Setting expectations for the ecological condition of streams: the concept of reference condition. Ecological Applications 16(4):1267-1276.
U.S. Environmental Protection Agency (EPA). 2005. Use of biological information to better define designated aquatic life uses in state and tribal WQS: Tiered aquatic life uses. EPA-822-R-05-001. U.S. Environmental Protection Agency, Office of Water, Washington, DC.