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Frequent Questions

What is CADDIS?

CADDIS, or the Causal Analysis/Diagnosis Decision Information System, is an online application designed to help users conduct causal assessments, primarily in stream ecosystems. It provides a logical, step-by-step framework for Stressor Identification based on the U.S. EPA’s Stressor Identification Guidance Document, as well as additional information and tools that can be used in these assessments.

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Why was CADDIS developed?

Thousands of water bodies in the United States are listed as biologically impaired. For many of these water bodies, the cause of impairment is reported as "unknown"—but before the TMDL process can be used to formulate appropriate management actions, the cause of biological impairment must be determined. Defensible causal analyses require knowledge of the mechanisms, symptoms, and stressor-response relationships for various stressors, as well as the ability to use that knowledge to draw appropriate conclusions. CADDIS was developed to provide users the information they need to conduct defensible causal assessments.

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Who developed CADDIS?

CADDIS is produced by the U.S. EPA’s Causal Analysis Team. Specific information for different sections of the site can be found on the Authors & Contributors page.

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Why did we call this site CADDIS?

The name CADDIS is an acronym, but it also is the common name of an order of insects called caddisflies (Trichoptera). Caddisfly larvae (see illustration at right) live in flowing waters on the bottom surfaces of streams. Many species live in tubes or cases they construct from sand, pebbles, leaves, and wood, held together by an adhesive substance that the larvae secrete. They drag the case with them as they move, with only their front ends and legs sticking out. They eat algae, decaying plant matter and microorganisms, and are eaten by many types of fish. Because many caddisfly species live only in high quality streams and decrease in abundance as stream quality declines, caddisflies are one type of organism that biologists often use to monitor the health of aquatic systems.

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How do I cite CADDIS?

U.S. EPA (Environmental Protection Agency). 2010. Causal Analysis/Diagnosis Decision Information System (CADDIS). Office of Research and Development, Washington, DC. Available online at https://www.epa.gov/caddis. Last updated September 23, 2010.

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How has CADDIS been updated in the 2010 release?

We have released the 2010 version of CADDIS to the public. The new release contains new content in each part of the site, and has been reorganized into five volumes, or topic areas. Listed below are those volumes, how they correspond to sections of the 2007 release (in parentheses), and the new content within each volume.

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Who should use CADDIS?

The CADDIS site contains technical information and was designed for use by scientists and engineers. However, much of the information on CADDIS may be useful for a wider audience as well (e.g., the modules providing background information on common sources and stressors).

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How do I use the CADDIS site?

CADDIS is a website designed to help users conduct causal assessments. It is organized into five volumes, each with distinct content & tools. If you are new to causal assessment, we recommend that you first review the Step-by-Step Guide Introduction in Volume 1, for an overview of the SI process described on the CADDIS site. Once you are familiar with causal assessment and the CADDIS site, you can move between volumes however you like, to view the information most helpful for answering your specific causal assessment questions.

The 2010 version of CADDIS was designed and tested using Internet Explorer version 7.0 with a screen resolution of 800 by 600 pixels. On many pages, CADDIS uses pop-up windows to provide supplemental information (e.g., additional text, enlarged images). A pop-up is a page or window that pops up when a link is selected. If you have problems viewing the pop-ups, please turn-off "disable pop-ups" in your browser (in Internet Explorer, use Tools: Internet Options: Privacy Tab) and be sure that JavaScript is enabled (in Internet Explorer, use Tools: Internet Options: Advanced Tab).

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How much data do I need to use CADDIS?

The Stressor Identification process outlined on CADDIS does not require a minimum data set, and existing data often are sufficient to determine the cause of an impairment. We recommend you review the section on Getting Started with data analysis to help you develop a sound foundation for your analysis. If the available data are too sparse to support a causal analysis, it may still be useful to go through the Stressor Identification process, but at a screening level, with the objective of identifying the data that would be most fruitful to collect. In addition, an important part of the process is evaluating whether the data used are of sufficient quantity and quality to support the causal analysis.

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Can I use CADDIS to determine causes of biological impairment in ecosystems other than streams?

The Stressor Identification process (and, by extension, the process outlined in the Step-by-Step Guide) is a general method for analyzing causes of detrimental biological effects. To date, the process primarily has been used for evaluating causal relationships in stream ecosystems. However, because it is based on fundamental principles of causal analysis, the process should be useful for causal assessments in any ecological system, and case studies have been completed in terrestrial systems.

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Can I use CADDIS to identify the source of a stressor causing biological impairment?

CADDIS will help you identify the stressor that is contacting or co-occurring with aquatic organisms in a way that causes detrimental changes. Identifying the sources of those stressors, developing and implementing management options, and monitoring restoration effectiveness are all important activities that technically are outside the scope of the CADDIS site. However, accurate and defensible identification of the cause is the key that directs management efforts toward finding solutions that have the best chance for improving biological condition, and the logic framework and tools provided on CADDIS can in some instances be applied to the source-to-stressor portion of the causal pathway.

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Can I print all or portions of the CADDIS site?

You can print out individual pages in CADDIS using the Print function on your web browser, and throughout the site certain sections may be available as separate pdf files (e.g., the Urbanization module, conceptual diagrams, etc.).

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What are the differences between causal analysis, the Stressor Identification (SI) process, and CADDIS?

A cause is something that brings about an effect or result. The analysis of causal relationships is central to everyday life and science, and it identifies the means by which we can improve our environment. The Stressor Identification (SI) Guidance Document provides a formal and rigorous process for identifying the stressors causing detrimental biological changes in aquatic ecosystems. The SI approach is based on three methods for evaluating causal relationships: refutation, diagnosis, and comparison of strength of evidence. CADDIS uses these three methods, but in a more integrated manner, and it emphasizes a step-by-step process for assembling and evaluating evidence. CADDIS also contains additional tools and resources to help in conducting causal assessments, as well as clarifications and updates developed since the SI Guidance Document was published.

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