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<br />Biological Data <br /> <br />The CDOW has conducted field surveys of the fishery resources on this stream and have found a <br />natural environment that can be preserved. As reported for this reach of stream in CDOW'S <br />recommendation letter to the CWCB, "The existence of a natural environment was established <br />by the CWCB in Case Number 4-84CW428. Bear Creek is classified as a medium stream <br />(between 20 to 35 feet wide). Aquatic sampling shows that a self sustaining brook and rainbow <br />trout fishery exists in the upper San Miguel River Basin. In addition to the trout fishery, the <br />upper basin also supports a population of mottled sculpins (See CDOW Fish Survey in Appendix <br />B). <br /> <br />Field Survey Data <br /> <br />CDOW and CWCB staff used the R2CROSS methodology to quantify the amount of water <br />required to preserve the natural environment to a reasonable degree. The R2CROSS method <br />requires that stream discharge and channel profile data be collected in a riffle stream habitat type. <br />Riffles are most easily visualized as the stream habitat types that would dry up first should <br />streamflow cease. This type of hydraulic data collection consists of setting up a transect, <br />surveying the stream channel geometry, and measuring the stream discharge. Appendix B <br />contains copies of field data collected for this proposed segment. <br /> <br />Biological Flow Recommendations <br /> <br />The CWCB staff relied upon the biological expertise of the cooperating agencies to interpret <br />output from the R2CROSS data collected to develop the initial, biologic instream flow <br />recommendation. This initial recommendation is designed to address the unique biologic <br />requirements of each stream without regard to water availability. Three instream flow hydraulic <br />parameters, average depth, percent wetted perimeter, and average velocity, are used to develop <br />biologic instream flow recommendations. The CDOW has determined that maintaining these <br />three hydraulic parameters at adequate levels across riffle habitat types, aquatic habitat in pools <br />and runs will also be maintained for most life stages of fish and aquatic invertebrates (Nehring <br />1979; Espegren 1996). <br /> <br />For this segment of stream, one data set was collected with the results shown in Table 1 below. <br />Table 1 shows who collected the data (Party), the date the data was collected (Date), the <br />measured discharge at the time of the survey (Q), the accuracy range of the predicted flows <br />based on Manning Equation (240% and 40% of Q), the summer flow recommendation based on <br />meeting 3 of 3 hydraulic criteria and the winter flow recommendation based upon 2 of 3 <br />hydraulic criteria. <br /> <br />Table 1: Data <br /> <br />Partv Date 0 250% -40% Summer (3/3) Winter (2/3) <br />DOW/CWCB 10/08/96 10.0 25.1-4.0 6.2 3.0(1) <br /> <br />BLM = Bureau of Land Management DOW = Division of Wildlife <br />(1) Predicted flow outside of the accuracy range of Malll1ing's Equation. <br /> <br />CWCB = Colorado Water Conservation Board <br />? = Criteria never met in R2CROSS Staging Table. <br /> <br />Biologic Flow Recommendations <br />The CDOW recommended a 6.2 cfs summer flow, based on the October 8, 1996, data collection <br />effort. Staff reviewed the data collected by the CDOW. The summer flow recommendation, <br />which meets 3 of 3 criteria and is within the accuracy range of the R2CROSS model is 6.2 cfs <br />(See Table 1). <br />