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41 OfJG150 (Burkhard, 1967; Weber, 1965) revealed that trout numbers and biomass statistics were from two to ten times higher below head- water diversions than on the same streams immediately above the diversions. These streams were resurveyed by the author again at the same sites in 1978, 14 years after the original investi- gations. The species composition and biomass ratios reconfirmed what was observed in 1964. Stable stream environments below the headwater diversions contained two to ten times the numbers and biomass of trout present in the same stream immediately above the diversions. The fact that the IFG3 Habitat Program consistently indicates that the greatest WUA exists at moderate flow rather than at peak flow levels gives biologists a powerful tool in assessing the potential impacts of both high water and low water levels. The one problem that remains to be evaluated is, what time span is required for these excessive water levels to have a real impact on the trout population and be reflected in the standing crop? Reliability and Comparability of Methodologies Output of predicted parameters from the single and multiple transect R-2 Cross and the IFG4 methods showed the greatest disparity when the average predicted velocities were compared. However, the most important comparison was with the recommended minimum flows from the three methodologies. These diff~r_~nce~ were not great in mO,B,tJnstances. ,Average depth showed great consistency among all methods tested and was the most often used parameter to delimit the minimum flow recommendation. Undoubtedly this was the primary reason for the similarities of the flow recommendations among the methods despite disparities between ,methodologies for average velocity. The reader is reminded that average depth and average velocity criteria were essentially the same for all three computer methods. Other investigators might disagree with the levels of these cri- teria as being too high or too low to delimit the proper minimum flow recommendation. This evaluation has shown that if the cri- teria are common to all methodologies. then si~ilar_minimum, flow recommendations are the result. Rose and Johnson (1976) found that to be the case in comparisons between the Montana, Forest Service, and Modified Sag-Tape methods on four streams in Utah.