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CADDIS Volume 2

Learn About Sources

What Are Sources?

Sources are activities, land uses or entities that directly or indirectly result in stressors. There currently is only one (1) source-based module in CADDIS, which considers urbanization and its effects on streams.

How Do Sources Relate to Candidate Causes?

A candidate cause is a hypothesized cause of a specific environmental impairment, sufficiently credible to be analyzed in a causal assessment.

A candidate cause can be simply a proximate stressor (e.g., low dissolved oxygen concentration), that is, the stressor directly responsible for the observed biological response (e.g., low dissolved oxygen concentration).

However, a candidate cause also may include more detailed information about the causal pathway, such as the source or sources that resulted in the proximate stressor (e.g., increased nutrients associated with stormwater runoff). Including more detail when listing candidate causes may help identify ways to distinguish among different candidate causes included in the assessment.