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CADDIS: A System to Help Investigators Determine the Causes of Biological Impairments in Aquatic Systems

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Over a thousand water bodies in the United States are listed by states as biologically impaired. For many of these, the cause of the impairment is also reported as “unknown”. Before an appropriate Total Maximum Daily Load (TMDL) can be formulated, the cause of the biological impairment, for example, excess fine sediments, nutrients, or toxic substances, must be determined. Defensible causal analyses require knowledge of the mechanisms, symptoms, and stressor-response relationships for various specific stressors as well as the ability to use that knowledge to draw appropriate conclusions. This paper describes the first version of the Causal Analysis/Diagnosis Decision Information System (CADDIS). CADDIS is a web-based decision support system that will help investigators in the regions, states and tribes find, access, organize and share information useful for causal evaluations in aquatic systems. It is based on the USEPA's Stressor Identification process, which is a formal method for identifying causes of impairments in aquatic systems. Current features of CADDIS include a step-by-step guide to conducting a causal analysis, downloadable worksheets and examples, a library of conceptual models, and links to helpful information. Future plans include modules on deriving empirical stressor-response relationships; stressor-specific tolerance values; and databases and syntheses of relevant literature on sediments and toxic metals. Future versions will be developed incrementally and iteratively, and frequent user input and feedback will be essential to the system's success.

Document Type: Research Article


Publication date: January 1, 2005

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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