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0 <br />Table 1: Data <br />i <br />Party <br />Date <br />Q <br />250 % -40% <br />Summer 3/3 <br />Winter 2/3 <br />BLM <br />09/29/2005 <br />13.5 <br />33.6-5.4 <br />6.2 <br />5.6 <br />BLM <br />09/29/2005 <br />15.2 <br />38.0-6.1 <br />8.0 <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 />Biologic Flow Recommendation <br />The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range <br />of the R2CROSS model is 7.1 cfs. This recommendation was produced by averaging the data <br />sets. The winter flow recommendation, which meets 2 of 2 criteria and is within the accuracy <br />range of the R2Cross model is 5.6 cfs. It is our belief that recommendations that fall outside of <br />the accuracy range of the model, over 250% of the measured discharge or under 40% of the <br />measured discharge may not give an accurate estimate of the necessary instream flow required. <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. While a historic gaging station was found downstream from the <br />proposed instream flow segment on the North Fork North Platte River, the gage is heavily <br />affected by diversions and has a period of record from 1923 to 1945. With so limited a record, it <br />was necessary to use indirect methods to define the stream's flow regime (the appendix contains <br />the summary of gage data for the two gages mentioned above). The hydrograph below was <br />produced using the USDI Geological Survey's StreamStats system. This methodology estimates <br />streamflow in ungaged basins through statistical analyses of selected watershed characteristics. <br />The StreamStats values for discharge represent the "natural" or undiminished flow of the basin. <br />However, water is diverted from the North Fork North Platte River above the point at which the <br />StreamStats analysis was made. To better estimate the actual (depleted) flows of North Fork <br />North Platte River, the mean monthly diversions (or consumptive use associated with upstream <br />diversions) was subtracted from the mean monthly stream flows of StreamStats. To do this it <br />was assumed that 1) consumptive use was 50% of the amount diverted, and 2) diversion occurred <br />during each day of the irrigation season month, for 24 hours a day. <br />Table 2 and Figure 1 below show that the recommended summer flow of 7.1 cfs is available on <br />average during the period of April 1 through July 31. Due to limited water availability, the <br />summer flow recommendation has been reduced to 4.5 cfs during the period of August 1 to <br />October 31. In addition, due to limited water availability, the winter flow of 5.6 cfs was reduced <br />to 2.8 cfs during the period of November 1 to March 31. <br />