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<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 3.4 cfs (See Table 1). This was derived by averaging the results of <br />the three data sets. The winter flow recommendation, which meets 2 of 3 criteria and is within <br />the accuracy range of the R2CROSS model is 1.0 cfs (See Table 1). It is our belief that <br />recommendations that fall outside of the accuracy range of the model, over 250% of the <br />measured discharge or under 40% of the measured discharge may not give an accurate estimate <br />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 staffs water availability analysis in more <br />detail. Table 2 below displays the estimated stream flow of West Fork Dry Creek. <br /> <br />Table 2 shows that for this reach, the summer flow recommendation of 3.4 cfs is available only <br />from April 1 to June 30. The summer flow recommendation was reduced to 0.85 cfs for the time <br />period of July 1 through July 31 based on limited water availability. The winter flow <br />recommendation of 1.0 cfs is not available at least 50% of the time. The winter flow <br />recommendation was reduced to 0.3 cfs for the period of August 1 to February 28, and to 0.85 <br />cfs from March 1 to March 31 based on limited water availability. <br /> <br />Table 2: Estimated Stream Flow on West Fork Dry Creek: <br />Jan Feb Mar Apr May Jun <br />(efs) 0.3 0.7 1.0 15.5 56.4 25.9 <br /> <br />Jul <br />1.3 <br /> <br />Aug Sep Oct <br />0.5 0.4 0.4 <br /> <br />Nay Dee <br />0.4 0.4 <br /> <br />-4- <br />