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. . . Miguel River near Ames. Dissolved levels of heavy metals in the Howard's Fork continue to be a problem for the river's fishery but conditions may be improving. Protection of the high quality water in the headwaters and all of the tributaries of the Howard's Fork is vital to the continued '- improvements we are seeing in both water quality and fish populations. Field Survey Data CDOW and CWCB staff used the R2Cross methodology to quantify the amount of water required to preserve the natural environment to a reasonable degree. The R2Cross method requires that stream discharge and channel profile data be collected in a riffle stream habitat type. Riffles are most easily visualized as the stream habitat types that would dry up first should streamflow cease. This type of hydraulic data collection consists of setting up a transect, surveying the stream channel geometry, and measuring the stream discharge. Appendix B contains copies of field data collected for this proposed segment. Biological Flow Recommendations The CWCB staff relied upon the biological expertise of the cooperating agencies to interpret output from the R2Cross data collected to develop the initial, biologic instream flow recommendation. This initial recommendation is designed to address the unique biologic requirements of each stream without regard to water availability. Three instream flow hydraulic parameters, average depth, percent wetted perimeter, and average velocity, are used to develop biologic instream flow recommendations. The CDOW has determined that maintaining these three hydraulic parameters at adequate levels across riffle habitat types, aquatic habitat in pools and runs will also be maintained for most life stages of fish and aquatic invertebrates (Nehring 1979; Espegren 1996). For these segments of stream, three data sets were collected with the results shown in Table 1 below. Table 1 shows who collected the data (Party), the date the data was collected (Date), the measured discharge at the time of the survey (Q), the accuracy range of the predicted flows based on Manning Equation (240% and 40% of Q), the summer flow recommendation based on meeting 3 of 3 hydraulic criteria and the winter flow recommendation based upon 2 of 3 hydraulic criteria. Table 1: Data Party Date Q 250%-40% Summer (3/3) Winter (2/3) DOW ICWCB 10109/96 2.22 5.5 -0.9 5.6 1.5 DOW/CWCB 10/09/96 14.8 37.0 - 5.9 4.6~1) 2.5~I) DOW/CWCB 10/09/96 11.2 28.0- 4.5 8.3 3.5(1) . . BLM = Bureau of Land Management DOW = DIVISIOn of WIldhfe (I) Predicted flow outside of the accuracy range of Manning's Equation. CWCB = Colorado Water ConservatIOn Board ? = Criteria never met in R2CROSS Staging Table. Biologic Flow Recommendations . The CD OW recommended a 5.6 cfs summer flow and a 1.5 cfs winter flow for the upper segment and a 8.3 cfs summer flow and a 3.0 cfs winter flow for the lower segment based on the October 9th, 1996, data collection efforts. Staff reviewed the data collected by the CDOW. The summer flow recommendation for the upper reach, which meets 3 of 3 criteria and is within the accuracy range of the R2CROSS model is 5.6 cfs. The winter flow recommendation for the upper reach which meets 2 of 3 criteria and is within the accuracy range of the R2CROSS model is 1.5 cfs (See Table 1). The summer flow recommendation for the lower reach, which meets 3 of 3 criteria and is within the accuracy range of the R2CROSS model is 8.3 cfs. The winter flow recommendations which meet 2 of 3 criteria both fall outside of the accuracy range of the - 5 -