You are here:
CONDITIONAL PROBABILITY ANALYSIS APPROACH FOR IDENTIFYING BIOLOGICAL THRESHOLD OF IMPACT FOR SEDIMENTATION: APPICATION TO FRESHWATER STREAMS IN OREGON COAST RANGE ECOREGION
Citation:
Paul, J F. AND M E. McDonald. CONDITIONAL PROBABILITY ANALYSIS APPROACH FOR IDENTIFYING BIOLOGICAL THRESHOLD OF IMPACT FOR SEDIMENTATION: APPICATION TO FRESHWATER STREAMS IN OREGON COAST RANGE ECOREGION. Presented at SETAC 2004, Portland, OR, November 11-18, 2004.
Description:
A conditional probability analysis (CPA) approach has been developed for identifying biological thresholds of impact for use in the development of geographic-specific water quality criteria for protection of aquatic life. This approach expresses the threshold as the likelihood of exceeding a given value of a pollution metric. Uncertainty and natural variability are inherently incorporated into the analysis. Application of this approach with survey data (probability-based sample design) allows extrapolation of the results to the entire geographic area and eliminates possible bias in site selection. Data came from streams in the Coast Range Ecoregion in Oregon. Benthic community index values (EPT taxa richness) were used to identify impacted stream communities. Several types of indicators of sedimentation (e.g., percent fines, mean particle size, and turbidity) were selected. For each indicator, thresholds of impact were identified by three different techniques. An example is provided of how these thresholds can be used to develop a criterion for protection of aquatic life in streams. Resulting thresholds were compared with thresholds identified with CPA for Mid-Atlantic wadable streams. Although final development of water quality standards requires a management decision, the development of scientifically-defensible approaches for establishing criteria based on significant deviations from expected community condition across a wide range of geographic conditions could be a useful first step in the process.