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<br />habitat provides plentiful pools to insure fish survival during low flow periods, The stream <br />environment occasionally experiences flash flooding, but the stream channel is stable, with a <br />well-established riparian community and well-anchored substrate, (See BLM Fish Survey in <br />Appendix B), <br /> <br />Field Survey Data <br /> <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 />discharge 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 /> <br />Biological Flow Recommendation <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 in stream 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, 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 /> <br />Table 1: Data <br /> <br />Partv Date Q 250% -40% Summer (3/3) Winter (2/3) <br />BLM 6/7/01 6,36 15,9 - 2,5 17,3") 10,7 <br />BLM 6/7/01 5,98 14,9 - 2.4 13.1 10,2 <br /> <br />BLM = Bureau of Land Management DOW = Division of Wildlife <br />(1) Predicted flow outside of the accuracy range of Manning's Equation. ? = Criteria never met in R2CROSS Staging Table. <br /> <br />Biologic Flow Recommendation <br />The summer flow recommendation, which met 3 of 3 criteria and is within the accuracy range of <br />the R2CROSS model is [3,0 cfs (See Table 1), The BLM did not make a winter <br />recommendation because of very limited water availability, <br /> <br />Hydrologic Data <br /> <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 />USGS stream gage for Horsefly Creek near Sams, CO (ID #09173500), which has a drainage <br />area of 28,8 square miles (See Gage Summary in Appendix C), The drainage area of the <br />- 3 - <br />