Tuesday, May 27, 2008
191

Analyzing causes of undesirable effects in streams using USEPA's CADDIS web site

Susan Norton, National Center for Environmental Assessment, U.S. EPA, 1200 Pennsylvania Ave. NW, (8623-P), Washington, DC 20460

Updates in 2007 to the USEPA’s Causal Analysis/Diagnosis Decision Information System (CADDIS, available on-line at http://www.epa.gov/caddis) add new information and analytical tools to the original framework for evaluating the causes of undesirable biological effects in aquatic systems.  The Candidate Cause module helps practitioners 1) choose what to list, what not to list and what to defer, based on sources, site information, and observed biological effects, 2) write reports by providing conceptual models and supporting text that can be copied or modified to explain the source-to-impairment pathways for an impaired site, and 3) make useful site observations in the field.  Commonly encountered causes of impairments to aquatic systems are reviewed: metals, sediments, nutrients, flow alteration, temperature, ionic strength, and low dissolved oxygen.  CADDIS includes Conceptual Models that illustrate the relationships from sources to stressors to biological effects.  An Interactive Conceptual Model  for phosphorus links the diagram with supporting literature citations. The Analytical Tools module helps practitioners analyze their data sets and interpret and use those results as evidence within the USEPA causal assessment process.  Downloadable tools include a GUI based statistical package (CADStat), programs for use with the freeware R statistical package, and a Microsoft Excel template.  These tools can be used to quantify associations between any cause and any biological impairment using innovative methods such as species-sensitivity distributions, biological inference indices, conditional probability analysis, and quantile regression analysis. The updates have grown the Web site from a causal analysis framework to a causal analysis worksite.

 Disclaimer:  The views expressed in this abstract are those of the author and do not necessarily reflect the view or policies of the U.S. Environmental Protection Agency



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