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<br />Part <br />DOW <br /> <br />Date <br />10/21/98 <br /> <br />27.3 <br /> <br />250% -40% <br />68.1 - 10.9 <br /> <br />Summer <br />39 <br /> <br /> <br />Winter 2/3 <br />21 <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 R2PRUDEN 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 range is 39 cfs (See Table 1). The winter flow recommendation, which <br />met 2 of 3 criteria and is within the accuracy range of the R2CROSS model is 21 cfs (See Table <br />1). <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 Anthracite Creek near Somerset, CO (ID #09132050), which has a <br />drainage area of 94.60 square miles (See Gage Summary in Appendix C). The total drainage <br />area of the Coal Creek Drainage is approximately 92 square miles. The period of record for this <br />gage was 1977 to 1981, the period of record used by staff in their analysis was 1977 - 1981, or 5 <br />years of record. Table 2 below displays the estimated flow of Coal Creek, in terms of a <br />percentage of exceedence. <br /> <br />Table 2: Estimated Stream Flow in Coal Creek: <br />Exeeedenees Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nav Dee <br />10/0 34.1 32.8 182.3 660.8 3616.6 1808.3 915.5 117.0 54.0 46.5 35.1 28.6 <br />50/0 22.5 24.6 67.4 540.4 1735.5 1669.2 573.5 98.2 47.1 32.6 27.8 23.3 <br />10% 21.4 23.5 51.6 498.6 1545.1 1498.0 497.6 88.3 40.7 28.9 27.8 22.5 <br />20% 20.3 21.4 40.7 374.5 1157.7 1230.5 374.5 77.0 34.2 26.8 25.7 21.4 <br />80% 16.1 17.1 22.5 43.9 281.6 626.0 41.7 23.5 21.4 18.2 18.2 17.1 <br />90% 15.0 16.1 21.4 34.2 232.2 240.8 26.2 20.3 20.3 18.2 17.1 16.1 <br />95% 15.0 15.0 20.3 30.0 194.7 204.4 24.6 19.3 19.8 17.1 16.1 15.0 <br />99% 13.1 13.9 19.3 27.0 174.1 151.3 22.5 17.1 18.2 15.0 16.1 13.4 <br /> <br />-4- <br />