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. . . other words, the water quality of nearly all of the San Miguel's tributary streams is extremely pure - pure to the point that electro fishing is not possible with standard electro fishing equipment. Fish may exist in these streams but they are not readily sampled with standard electro fishing gear. The CD OW believes that the lower reaches of these streams are used by fish that are residents of the mainstem of the Howard's Fork San Miguel River and are important to the overall fish community during some periods of the year (i.e. spawning, rearing, and refugia from high flow events). CDOW also believes that the high quality water that is produced by the tributary streams is extremely important to the impaired water quality of the Howard's Fork San Miguel River. Mine drainage into the Howard's Fork San Miguel River and mill tailings piles adjacent to the river are currently being cleaned up as a result of several small scale reclamation efforts above the confluence with the South Fork of the San Miguel River. Dissolved levels of heavy metals in the Howard's Fork continue to be a problem for the river's fishery but conditions are improving; the high quality water from tributary streams such as Chapman Gulch are vital to the continued improvement of water quality and the Howard's Fork's fish population. 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 this segment of stream, one data set was 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/CWCB 10/09/96 1.64 4.1 - 0.7 4.8(1) 1.8 . . . BLM = Bureau of Land Management DOW = DIVISIon of WIldlife CWCB = Colorado Water ConservatIOn Board (I) Predicted flow outside of the accuracy range of Manning's Equation. ? = Criteria never met in R2CROSS Staging Table. - 3 -