Assessing biological integrity in running waters : a method and its rationale

A recent nationwide USEPA study found that 56% of the stream segments with water resource degradation had a reduced fishery potential because of chemical problems however, 50% were impaired by degradation in physical habitat and 67% by flow alteration (Judy et al. 1984). In short, halting the chemical degradation of water does not of itself assure the restoration of its ecological or biotic integrity. The ability of a water resource system to sustain a
\nbalanced biological community is obviously the best indicator of its potential; yet that ability is largely unprotected by present monitoring and assessment techniques.