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. . ~.r' Biological Data The CDOW has conducted field surveys of the fishery resources on this stream and have found a natural environment that can be preserved. As reported for this Teach of stream in CDOW'S recommendation letter to the CWCB, "The existence of a natural environment was established by the CWCB in Case Number 4-84CW428. Bear Creek is classified as a medium stream (between 20 to 35 feet wide). Aquatic sampling shows that a self sustaining brook and rainbow trout fishery exists in the upper San Miguel River Basin. In addition to the trout fishery, the upper basin also supports a population of mottled sculpins (See CDOW Fish Survey in Appendix B). Field Survey Data CDOW and CWCB staff used the R2CROSS methodology to quantify the amount of water required to pTeserve the natural environment to a reasonable degree. The R2CROSS method requiTes that stream discharge and channel profile data be col1ected in a rime stream habitat type. Rimes are most easily visualized as the stream habitat types that would dry up first should streamflow cease. This type of hydraulic data col1ection consists of setting up a transect, surveying the stream channel geometry, and measuring the stream dischaTge. Appendix B contains copies of field data col1ected for this proposed segment. Biological Flow Recommendations The CWCB staff relied upon the biological expertise of the cooperating agencies to interpret output from the R2CROSS data col1ected 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 rime 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 col1ected with the Tesults shown in Table I below. Table I shows who col1ected the data (Party), the date the data was col1ected (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 summer 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 DOWICWCB Date Q 10108196 10.0 250%-40% 25.1-4.0 Summer (3/3) 6.2 Winter (2/3) 3.0(1) BLM Bureau of Land Management DOW Division of Wildlife (I) Predicted flow outside of the accuracy range of Manning's Equation. ewes - Colorado Water Conservation Board ? = Criteria never met in R2CROSS Staging Table. Biologic Flow Recommendations The CDOW Tecommended a 6.2 cfs summer flow, based on the October 8,1996, data col1ection effort. Staff reviewed the data col1ected by the CDOW. The summer flow Tecommendation, which meets 3 of 3 criteria and is within the accuracy range of the R2CROSS model is 6.2 cfs (See Table 1).