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optimal cover are limiting tors for fish habitat, underscoring the ~ortance of adequate flows <br />to prevent further stress to the fishery. Because of some natural stream barriers, the stream <br />provides good habitat for Colorado River Cutthroat Trout" (see CDOW Fish Survey in Appendix <br />B). <br />Field Survey Data <br />BLM staff used the R2Cross methodology to quantify the amount of water required to preserve <br />the natural environment to a reasonable degree. The R2Cross method requires that stream <br />dischazge and channel profile data be collected in a riffle stream habitat type. Riffles are most <br />easily visualized, as the stream habitat types that would dry up first should streamflow cease. <br />This type of hydraulic data collection consists of setting up a transect, surveying the stream <br />channel geometry, and measuring the stream discharge. Appendix B contains copies of field <br />data collected for this proposed segment. <br />Biological Flow Recommendation <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 aze 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 />For this segment of stream, two data sets were 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 />Table 1: Data <br />Part Date Q 250%-40% Summer (3/3) Winter 2/3 <br />BLM 8/29/1996 10.97 27.4 - 4.4 25.1 2.4 <br />BLM 9/27/2002 10.45 26.1 - 4.2 23.1 13.5 <br />tSLM = t5ureau of Lantl Managgement llU W = Urvtsion of Wildlife <br />(1) Redicted flow outside of [he accuracy range of Manning's Equation. ? =Criteria never me[ in R2CAOSS Staging Table. <br />Bioloeic Flow Recommendation <br />The summer flow recommendations, which meet 3 of 3 criteria and are within the accuracy range <br />of the R2CROSS model are 25.1 and 23.1 cfs (See Table 1). The winter flow recommendation, <br />which meets 2 of 3 criteria and is inside the accuracy range of the R2CROSS model is 13.5 cfs <br />(See Table 1). Averaging the two summer flow recommendations within range results in a 24.1 <br />cfs recommendation. <br />Hydrologic Data <br />After receiving the cooperating agency's biologic recommendation, the CWCB staff conducted <br />an evaluation of the stream hydrology to determine if water was physically available for an <br />instream flow appropriation. The hydrograph below was derived from data collected by the <br />-3- <br />