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supports a self-sustaining brook trout fishery. Substrate, water quality, pools, and cover are excellent for salmonids, However, poor channel and bank stability, because of occasional large flow events, are limiting factors for fish habitat, underscoring the importance of adequate flows to prevent further stress to the fishery" (see CD OW Fish Survey in Appendix B). Field Survey Data BLM staff used the R2Cross methodology to quantify the amount of water required to preserve the natural environment to a reasonable degree. The R2Cross method requires that stream discharge and channel profile data be collected in a riffle stream habitat type. Riffles are most easily visualized, as the stream habitat types that would dry up first should streamflow cease. This type of hydraulic data collection consists of setting up a transect, surveying the stream channel geometry, and measuring the stream discharge. Appendix B contains copies of field data collected for this proposed segment Biological Flow Recommendation The CWCB staff relied upon the biological expertise of the cooperating agencies to interpret output from the R2Cross data collected to develop the initial, biologic instream flow recommendation. This initial recommendation is designed to address the unique biologic requirements of each stream without regard to water availability. Three instream flow hydraulic parameters, average depth, percent wetted perimeter, and average velocity are used to develop biologic instream flow recommendations. The CDOW has determined that maintaining these three hydraulic parameters at adequate levels across riffle habitat types, aquatic habitat in pools and runs will also be maintained for most life stages of fish and aquatic invertebrates (Nehring 1979; Espegren 1996). For this segment of stream, one data set was collected with the results shown in Table 1 below. Table 1 shows who collected the data (Party), the date the data was collected (Date), the measured discharge at the time of the survey (Q), the accuracy range of the predicted flows based on Manning Equation (240% and 40% of Q), the swnrner flow recommendation based on meeting 3 of 3 hydraulic criteria and the winter flow recommendation based upon 2 of 3 hydraulic criteria, Table 1: Data Party BLM Date 9/01/1999 Q 2.85 250%-40% 7.1 --- Ll Summer (3/3) 2.4 Winter (2/3) Ll BLM Bureau of Land Management DOW Division of Wildlife (1) Predicted flow outside of the accuracy range of Manning's Equation. ? = Criteria never met in R2CROSS Staging Table. Biologic Flow Recommendation The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range of the R2CROSS model is 2.4 cfs (See Table I). The winter flow recommendation, which meets 2 of3 criteria and is within the accuracy range of the R2CROSS model is Ll cfs (See Table I). Hydrologic Data After receiving the cooperating agency's biologic recommendation, the CWCB staff conducted an evaluation of the stream hydrology to determine if water was physically available for an instream flow appropriation. The hydro graph below was derived using a basin apportionment method from data collected by the USGS stream gage for East Rifle Creek near Rifle, CO (ill #09091500), which has a drainage area of 34.3 square miles (See Gage Summary in Appendix C). The total drainage area of the Butler Creek Drainage upstream of George Creek IS - 3 -