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What’s Wrong with Your Stream? Ask CADDIS!

Man fishing

Often, it’s not hard to tell that your local stream, lake, or wetland is in trouble. Perhaps an advancing carpet of thick, green algae is engulfing the rocks and logs, darkening the water, and making everything slick to the touch. Periodic fish kills or the seemingly sudden disappearance of certain species of aquatic insects are other unwelcome signs that things are amiss. Finding the cause of such problems, called “biological impairments,” however, is a real challenge.

State environmental agencies list more than 1,000 water bodies across the country as biologically impaired. Frequently, the cause of a biological impairment is unknown. The U.S. Environmental Protection Agency is working to help identify the causes of impairments through a web-based application called the Causal Analysis/Diagnosis Decision Information System, or CADDIS.

CADDIS provides scientists and engineers an online tool for performing step-by-step analyses, complete with worksheets and real-world field examples, to find, access, and share environmental information that identifies potential causes of trouble in their local waterways. The tool is designed to guide users through a formal, rigorous process that organizes scientific evidence to support conclusions.

Susan Norton, an ecologist in EPA’s National Center for Environmental Assessment who helped develop CADDIS, says “we provide a clear and consistent method to identify and compare candidate causes of impairment.” Norton goes on to explain how this is a critical first step in any effort to implement solutions and practices to restore water quality in streams and other water bodies.

What’s in a name?

What’s in a name? CADDIS got its name from Caddisflies, or Trichoptera, a group of aquatic insects. Because caddisflies thrive only in clean, healthy habitats, biologists keep an eye on their population levels to monitor the overall health of the habitat.

In the case of the polluted Naugatuck River, Lee Dunbar of the Connecticut Department of Environmental Protection praises CADDIS for providing “a clear, easily understandable format” for explaining and supporting conclusions about the river to both scientists and nonscientists. The CADDIS process helped environmental managers engage both elected officials and the public when setting target pollution levels to help clean up the river.

Other states have now gotten into the act, and EPA is using these real-world experiences to continually add to the CADDIS database and case studies. This built-in feedback mechanism means that the tool will grow as more is learned about identifying the causes of biological impairment in local waterways. As this happens, the number of streams in the “unknown cause” category will shrink, giving watershed managers and others more tools in their effort to clean up the nation’s waterways.

Want to know more about CADDIS? Aquatic biologists, TMDL coordinators, environmental scientists and engineers, watershed coordinators and others who are interested in giving CADDIS a try, or providing review comments to further improve CADDIS, are encouraged to contact serveiss.victor@epa.gov.

CADDIS Web site | Writer Aaron Ferster

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