Can instream flow requirements protect biodiversity?

In many areas of the U.S., population growth is prompting regulatory authorities and others to search for practicable instream flow policies that can protect stream ecological integrity in the face of increasing human demands for water. A central aspect of ecological integrity is maintaining the full diversity of biota native to a system.  Studies of stream fishes and invertebrates in the eastern U.S. and elsewhere have shown depressed species richness and occurrences in relation to increased capacities for water diversion from streams, stream system fragmentation, and accentuated short-term flow variability.  These findings support incorporating multiple elements into instream flow regulations - e.g., limits on relative size of diversions, on fragmentation by reservoirs, and on pumping regimes that result in frequent and rapid changes in stream flow. Additionally, other factors, such as water quality and stream geomorphology, are expected to interact with flow changes in influencing biotic condition.   Landscape-scale analyses capable of incorporating relevant environmental drivers into predictive models offer a useful framework for evaluating alternative stream management scenarios, and for answering the question posed by the title.