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000005 Stream Health It is clear from the legal elements of CWA that useful Stream Health analysis has to be based on biological integrity and not on just physical or chemical parameters. In addition to degraded habitat (the focus of this brochure), the introduction of non-native species, overharvest, and/or the fragmentation of habitat also playa major role in the loss of biological integrity. Given this complexity, the Stream Health definitions used by the Forest Service have evolved over several years in cooperation with EPA, State water quality agencies, and other federal resource agencies. The final result has two analytical scales: DIVERSITY, as an integration of ecosystem diversity and stability, and PRODUCTIVITY, as a ratio of existing (or expected) productivity compared to the long-term natural productivity. The DIVERSITY definitions* and class names are as follows: Robust Comparable to the best situations unaltered by humans; all regionally expected species for the habitat and water body size, including the most intolerant forms, are present with a full array of age and sex classes; balanced trophic structure. CWA standard. Adequate Fish and macroinvertebrate species richness is somewhat less than the best expected, especially due to loss of most intolerant forms; some fish species have less than optimal abundances or size distributions; trophic structure shows some sign of stress. Diminished Fewer intolerant forms of fish and macroinvertebrates are ----- present. Trophic structure of the fish community is more skewed toward an increasing frequency of omnivores; older age classes of top carnivores may be rare. Diminished < Adequate < Robust. Impaired Fish community is dominated by omnivores; pollution tolerant forms and habitat generalists; few top carnivores; growth rates and condition factors commonly depressed; hybrids and diseased individuals may be present. Pollution tolerant macroinvertebrates are often abundant. Impaired < Diminished. Precarious Few fish present, mostly introduced or very tolerant forms; hybrids common; disease, parasites, physical damage, and other anomalies regular. Only tolerant macroinvertebrate forms present. Catastrophic No fish, very tolerant macroinvertebrates, or no aquatic life. * EPA. 1983. Technical Support Manual: Waterbody Surveys and Assessments for Conducting Use Attainability Analyses. Office Water Regulations & Standards, Wash, DC. 20460. Pg V-4. (EPA names were changed to these class descriptions.) ============================================================================== Text Page 3 D'.' ~.