Evaluation of Instream Flow Methods and Determination

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8 e Chronological Order of Data Analysis The contract stated that each methodology should be evaluated individually, step by step and with as little bias as possible occurring between methods. The primary investigator and the field crew under his supervision collected all of the field data, thereby at least maintaining a constant source of error and hopefully as small an error as possible. The field data for the R-2 Cross analysis process was turned over to the Ecological Services Section of the DOW for computer analysis and determination of minimum flows by the Single Transect R-2 Cross Hethod. This was done without any assistance or input from the primary investigator. After the single transect R-2 Cross m1n1mum flow recommendations were made by Ecological Services, all R-2 Cross data were then turned over to the primary investigator for the multiple transect R-2 Cross analysis and minimum flow determination process, without the primary investigator's knowledge of what the single transect R-2 Cross minimum flow determination was. Finally, these sets of data (single and multiple transect cross section R-2 Cross analysis) were set aside and the IFG4 analysis was completed using average velocity and average depth as the two criteria for making minimum flow recommendations. e The Tennant or Montana Method was the fourth method used and is a synthetic analysis based on mathematical manipulation of U.S.G.S. gaging data as described by Tennant (l97S). Thirty percent of the average discharge, which Tennant classifies as an excellent flow for the needs of fish and aquatic invertebrates, was the level used in this study for comparative purposes between methods. The last method of analysis was the IFG3 or "weighted usable area" model (Bovee and Cochnauer, 1977) which interfaces with both the IFG4 Incremental Method and the Wetted Surface Profile (WSP) or IFG2 Hethod. In this study, the IFG3 was interfaced with the IFG4 Hethod, but not in the traditional sense for setting minimum flow recommendations. Rather, weighted usable area for all life stages was analyzed to determine if the model predictions were reflected in the actual species composition of the fish population observed through electroshocking studies. Population Estimation Methodologies Trout population density and biomass estimates were completed using the standard Petersen Mark and Recapture method with two electro- shocking runs through the stream. In most instances 24 hours of time elapsed between the first pass for marking and the second (recapture) pass. However, on the small streams with less than 10 cfs discharge the second pass was made the same day. e tt I ~ t ~ 1 i , ~ i I I I 1 i !