Biological Indicators of Watershed Health

The presence, condition, and numbers of the types of fish, insects, algae, plants and other aquatic life can provide accurate information about the health of a specific waterbody such as a river, stream, lake, wetland, estuary or coral reef.

Biological assessments are used to evaluate the condition of a water body using direct measurements of the resident biota in surface waters and integrate the cumulative impacts of chemical, physical, and biological stressors on aquatic life (see Using Biological Data as Indicators of Water Quality (PDF, 237KB). Biological criteria, derived from biological assessment information, can be used to define State and Tribal water quality goals for aquatic life by directly characterizing the desired biological condition for an aquatic life use designation and evaluating if a water body is attaining that use (see Overview of Process To Assess WQS Attainment and Identify Impaired Waters (PDF, 729KB) .

In summary, biological information provide a direct measure of the desired condition of the aquatic biota. This capability serves a dual purpose—goal setting and environmental impact analysis.

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