New EPA tool for determining cause of ecological harm to rivers and streams

Posted February 2006

To improve the nation's waters, the U.S. Environmental Protection Agency (EPA) has released a new web-based tool, the Causal Analysis/Diagnosis Decision Information System (CADDIS), which simplifies determining the cause of contamination in impaired rivers, streams, and estuaries. An impaired body of water does not meet the state or federal water quality standards for one or more pollutants.

More than a thousand U.S. water bodies have been identified as impaired, and in many cases, the cause is unknown. There are many possible sources of pollution such as industrial waste, municipal sewage, agricultural runoff, naturally occurring minerals in rock and sand, and biological materials. Before restorative or remedial actions can be taken, the cause of impairment must be determined.

CADDIS provides a standardized and easily accessible system to help scientists find, use, and share information to determine the causes of aquatic impairment. Causal analyses look at stressor-response relationships, meaning the effect of a specific substance or activity (stressor) on the environment. Typical water stressors include excess fine sediments, nutrients, or toxic substances.

This version of CADDIS is the first of three. Future versions will include modules to quantify stressor-response relationships, and databases and syntheses of relevant literature on sediments and toxic metals. CADDIS is available on EPA's web pages and can be accessed by clicking here.