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. . " " 27 Quantification of the amount of water deemed necessary to "preserve the natural environment to a reasonable degree" is becoming more challenging as Colorado's ISF Program expands into areas of greater water development pressure. This phenomenon became increasingly apparent last year when the CWCB narrowly averted a lengthy contested hearing on its proposed rSF appropriations on Fourmile Creek near the cities of Cripple Creek and Canon City. In addition, questions are also beginning to surface concerning the level of environmental protection that is provided under Colorado's ISF Program. For example, the Bureau of Land Management has proposed that an additional level of protection may be required for the reaches of the San Miguel River slated for consideration by the Board in 2002. In response to those questions and concerns, the CWCB staff has prepared the following recol1ll1lendations regarding quantification of biologic rSF recol1ll1lendations. SUl!l!estions for Develooinl! 'SF Recommendations on Cold Water Stream Reaches The single transect R2CROSS methodology has been the Board's primary quantification method for developing instream flow recol1ll1lendations on coldwater stream segments throughout the State of Colorado. The single transect, R2CROSS method is advantageous because (1) data acquisition is much more cost effective than other field-based methods, (2) the procedures are very easy to leam and implement, and (3) data interpretation is simple. In addition, the CWCB staff believes that recol1ll1lendations from field-based methods, like R2CROSS, are generally more representative of site- specific stream conditions than office-based methods like Tennant which are based on stream hydrology alone. The R2CROSS method has also been found to produce biologic flow recol1ll1lendations that are very similar to, and more cost effective than, recol1ll1lendations developed from more data intensive techniques (Nehring 1979). Finally, the hydraulic criteria that are used to develop R2CROSS-based instream flow recommendations were specifically designed to protect the biologic flow needs of cold water fish species within rime habitats (Nehring 1979). However, as indicated previously, the Fourmile Creek ISF recommendations were quite contentious and successful completion ofthese appropriations hinged on the development of biologic recol1ll1lendations that were based on the average of multiple R2CROSS data sets. The use of multiple R2CROSS datasets provided an opportunity for all participants in the ISF appropriation process to submit their data for consideration in the development of the resulting recommendation. Based on the success of the Fourmile Creek appropriation process, the CWCB staff recommends that the R2CROSS multiple transect, averaging approach be adopted as the Board's "standard" biologic quantification procedure for controversial !SF appropriations on coldwater streams. In support of this recommendation, the CWCB staff suggests that determining the. amount of water necessary to preserve the natural environment to a reasonable degree is similar to most other natural resource sampling problems. Staff believes that R2CROSS provides an objective, repeatable methodology to quantitY the unique flow requirements of individual stream reaches. Determining the number of samples that are required to characterize the biologic requirements of a stream reach will be dependent on the complexity of the habitats found within that particular stream segment. While characterization of the biologic requirements of simple, uniform stream reaches may only require R2CROSS data from a single transect, more complex stream reaches are likely to require data from several transects. Staff also believes that the R2CROSS multiple transect averaging approach aids in the resolution of opposed ISF appropriations because it allows all contesting parties to submit additional R2CROSS data for consideration during the resolution process. . While staffbelleves that the Board should adopt the single/multiple R2CROSS transect averaging approach as it's "standard" biologic quantification procedure for ISF appropriations on coldwater streams, it also 2