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<br />BLM = Bureau of Land Management DOW = Division of Wildlife <br />(1) Predicted flow outside of the accuracy range of Malll1ing's Equation. ? = Criteria never met in R2CROSS Staging Table. <br /> <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 7.3 cfs (See Table 1). This recommendation was derived by <br />averaging the results of the two data sets. The winter flow recommendation, which meets 2 of 3 <br />criteria and is within the accuracy range of the R2CROSS model is 5.3 cfs (See Table 1). It is <br />our belief that recommendations that fall outside of the accuracy range of the model, over 250% <br />of the measured discharge or under 40% of the measured discharge may not give an accurate <br />estimate of the necessary instream flow required. <br /> <br />Hydrologic Data <br /> <br />After receiving the cooperating agency's biologic recommendation, the CWCB and BLM staff, <br />conducted an evaluation of the stream hydrology to determine if water was physically available <br />for an instream flow appropriation. Although there is a substantial amount of streamflow gage <br />data available for the Uncompahgre Plateau and Glade Park, most of this data is severely <br />impacted by diversions and irrigation use. This situation makes it difficult to estimate the natural <br />flow regime for the watersheds on the Plateau. Without specific gage data to evaluate, the next <br />best approach is a regional equation that estimates annual flow characteristics. The USGS has <br />developed regional equations (Estimation of Natural Streamflow Characteristics in Western <br />Colorado. Water Resources Investigations Report 85-4086. 1985) that apply to the Uncompahgre <br />Plateau and Glade Park based on basin drainage area, mean annual precipitation, mean basin <br />elevation and mean basin slope. The report "Uncompahgre Plateau and Glade Park Annual <br />Hydrograph Estimation" in Appendix C, explains staff's water availability analysis in more <br />detaiL Table 2 below displays the estimated stream flow of Dry Creek. <br /> <br />For this reach, the synthetic hydrograph shows that the summer flow recommendation of 7.3 cfs <br />is available only from April 1 to June 30. The summer flow recommendation was reduced to 3.0 <br />cfs for the time period of July 1 through July 31 based on limited water availability. The winter <br />flow recommendation of 5.3 cfs is not available at least 50% of the time. The winter flow <br />recommendation was reduced to 1.2 cfs for the period of August 1 to February 28, and to 3.0 cfs <br />from March 1 to March 31 based on limited water availability. <br /> <br />Table 2: Estimated Stream Flow on Dry Creek: <br />Jan Feb Mar <br /> <br />Jun <br /> <br />Jul <br /> <br />Oct <br /> <br />Nav <br /> <br />Dee <br /> <br />(cfs) <br /> <br />-4- <br />