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INTRODUCTION Habitat loss is one of the single greatest causes of declines in populations of native fishes in North America (Williams et al. 1989). While there clearly must be some minimum flow needed to maintain a healthy, functioning river community, methods to establish minimum flows have proved controversial. Most flow studies implemented in Colorado have focused on protecting cold water habitats and use either the R2Cross method (Nehring 1979) or Instream Flow Incremental Methodology (IFIM) (Bovee 1982), which determines habitat availability based on a single target species. IFIM estimates the amount of usable habitat for fish as a function of discharge by combining habitat suitability curves with the hydraulic model. The habitat component of the model has received much criticism because of assumptions implicit with using suitability curves and assumptions of positive relationships between habitat availability and fish abundance. Validation of these assumptions have been obstacles for successfully using IFIM to model minimum flow impacts on large warm water rivers of the west slope (Rose and Hahn 1989). Warm water fish assemblages appear to require a more intensive approach to instream flow modeling compared to cold water fish communities. Warm water stream sections tend to have higher species diversity. Also habitat suitability curves derived from microhabitat observations do not adequately describe habitat use for many warm water species. A broad community-level perspective, as opposed to an indicator species approach, may be required to protect all habitats of a functioning warm water stream ecosystem. Instream flow techniques require integration of two processes that combine detailed knowledge of habitat requirements (by species and life stage), and the availability of necessary habitats. Both the collection and analysis of these data bases :. 1