Tuesday, May 19, 2009
186

Advantages of a statewide database for developing evidence in a watershed causal assessment

Susan M. Cormier1, Jeffrey Bailey2, Ben Lowman2, Jeroen Gerritsen3, and Lei Zheng3. (1) National Center for Environmental Assessment, US EPA, 26 W. Martin Luther King Dr., Cincinnati, OH 45268, (2) Division of Water and Waste Management, West Virginia Department of Environmental Protection, 601 57th Street, Charleston, WV 25304, (3) Tetra Tech Inc., 400 Red Brook Boulevard, Suite 200, Owings Mills, MD 21117

The USEPA Stressor Identification process was used to identify causes of biological impairment in the Clear Fork Watershed, West Virginia.  The State’s comprehensive database was quantitatively analyzed to develop evidence using: geographic tools, scatter plots with Spearman correlation, non-metric multi-dimensional scaling, ordinary linear regression, local weighted polynomial regression, deviance reduction changing point analysis (regression tree), conditional probability, and logistic regression.  Types of evidence included co-occurrence of stressors with observed biological impairment; plausible causal pathways, stressor-response threshold values from the statewide data analysis, and predictive models to rank multiple stressors.  Probable causes differed among tributaries in the watershed: metal contamination and acidification from mine drainage, aluminum toxicity in association with moderately acidic pH, sediment deposition, low dissolved oxygen, and organic enrichment from direct releases and from algal productivity enhanced by nutrients.  In the mainstem, combined causes impaired the river although dilution and different geophysical attributes reduced the effect.  The Clear Fork study showed that stressor-response associations from state-wide data clarify causal relationships of interconnected waterbodies in a watershed. 


Web Page: causal assessment, stressor-response relationships, casual evidence

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