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<br />e) <br /> <br />. <br /> <br />. <br /> <br />Biological Flow Recommendations <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 instream 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 />Part <br />DOW/CWCB <br /> <br />DOW <br /> <br /> <br />250%-40% <br />44.5 - 7.1 <br />9.9 - 1.6 <br /> <br />Winter 2/3 <br />4.0 <br />0.7 <br /> <br />Date Q <br />10110/96 17.8 <br />10/01198 4.0 <br /> <br />BLM = Bureau of Land Management DOW = Division of Wildlife <br />(I) Predicted flow outside of the accuracy range of Manning's Equation. <br /> <br />CWCB = Colorado Water Conservation Board <br />? = Criteria never met in R2CROSS Staging Table. <br /> <br />Biologic Flow Recommendations <br />The CDOW recommended a 6.7 cfs summer flow and a 2.4 cfs winter flow based on the October <br />10th, 1996, and October 1 st, 1998, data collection efforts. <br /> <br />Staff reviewed the data collected by the CDOW. The summer flow recommendations for the <br />reach, which meet 3 of 3 criteria and are within the accuracy range of the R2CROSS model <br />range between 10.9 cfs and 2.5 cfs. Averaging the two recommendations gives a 6.7 cfs summer <br />flow. The winter flow recommendations which meet 2 of 3 criteria both fall outside of the <br />accuracy range of the R2CROSS model (See Table 1). It is our belief that recommendations that <br />fall outside of the accuracy range of the model, over 250% of the measured discharge or under <br />40% ofthe measured discharge may not give an accurate estimate of the necessary instream flow <br />required. In these cases, CWCB staff relies upon the biological expertise of the cooperating <br />agencies to develop a biologic instream flow recommendation. <br /> <br />The CDOW has indicated that this is a high priority stream segment to them. However, because <br />the winter recommendations fall outside the accuracy range of the R2CROSS model, staff <br />believes that more data needs to be collected to accurately predict the winter flow <br />recommendation. To determine the winter flow recommendation, staff considered the proposed <br />winter recommendations of 4.0 and 0.7 cfs. Averaging the two recommendations gives a winter <br />recommendation of 2.4 cfs. After consulting with the Colorado Division of Wildlife, staff <br />believes 2.4 cfs will be sufficient to protect the natural environment to a reasonable degree, if <br />water is available (See Table 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 />