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39 O;}O;.~9 Requirements for Methodology Improvement - IFG4 The IFG4 model worked very well on the majority of the study streams evaluated in this study. Two situations required data manipulation for a satisfactory response from the IFG4 model. First, in those instan~es_where the calibration flows were very closely spaced, significant problems with the velocity adjustment !a~tors were encountered which required manipulation of the data, to "improve" the output. This occurred in only~!.e!!_instances and on relatively small mountain streams. Secondly, on larger streams (average discharge greater than 100 cfs) the only problems with the IFG4 model response to the data occurred where large boulders were strewn throughout the transect and the velocity profile varied greatly across the channel over very short dis- tances. Modification of the program to handle large velocity variations across the transect(s) would greatly increase the range and capability of the IFG4 program. The IFSG should modify the printout capability of the IFG4 program to give an average velocity, average depth, and total cross sectional area for each input Q at each transect. Then these parameters could be readily compared with the same output parameters of other methodologies. The lack of this capability required an additional 200 man-hours of hand calculations by t~e author in order to make direct comparison between the R-2 Cross and IFG4 methodologies. Recalling that the average velocities predicted by the IFG4 Method were underestimated by 2.0%, 67% of the time, the_ question arises as to why this is the case. It is probably something inherent in the program and could very well have some- thing to do with the velocity adjustment factor and the manipu- lation of the data inherent to that parameter. Some attempt should be made to correct this problem. Requirements for Methodology Improvement - IFG3 I believe giving equal weight to all of the preference factors for each life stage when the IFG4 Model is interfaced with the IFG3 model is wrong, especially for brown trout. Several in- vestigators have shown that overhead cover is the overriding factor in determining brown trout habitat, much more so than either depth or water velocity (Baldes and Vincent, 1969; Butler and Hawthorne, 1968; Elser, 1968; and Wesche, 1974). It is encouraging to know that a cover preference factor will soon be an input with the IFG3 model, but it should be given a heavier weighting in the calculation of weighted usable area. Finally, preference factors for cutthroat trout may not be reliable for the species in the streams studied, especially the Rio Grande cutthroat trout, Salmo claPki virginalis. Streams