Laserfiche WebLink
<br />Biological Data <br /> <br />The BLM has conducted field surveys of the fishery resources on this stream and have found a <br />natural environment that can be preserved. As reported in the letter from BLM to the CWCB <br />"Fishery surveys indicate that the stream environment is presently in stable and improving <br />condition, and supports a self-sustaining Colorado River Cutthroat Trout fishery. Channel <br />stability, bank stability, and substrate are good for salmonids. This type of stream environment <br />has steep gradients that typically limit the available pool habitat and food supply. In addition the <br />fishery is limited by occasional low flows. Accordingly, it is important to provide stream flows <br />that protect the limited amount of available habitat if the continued existence of the fishery is to <br />be assured" (See BLM Fish Survey in Appendix B). <br /> <br />Field Survey Data <br /> <br />BLM staff used the R2Cross methodology to quantify the amount of water required to preserve <br />the natural environment to a reasonable degree. The R2Cross method requires that stream <br />discharge and channel profile data be collected in a riffle stream habitat type. Riffles are most <br />easily visualized, as the stream habitat types that would dry up first should streamflow cease. <br />This type of hydraulic data collection consists of setting up a transect, surveying the stream <br />channel geometry, and measuring the stream discharge. Appendix B contains copies of field <br />data collected for this proposed segment. <br /> <br />Biological Flow Recommendation <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 CD OW 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, three data sets were collected with the results shown in Table 1 <br />below. 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's Equation (240% and 40% of Q), the summer flow recommendation based <br />on 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 />Party Date Q 250%-40% Summer (3/3) Winter (2/3) <br />BLM 8/15/1995 0.11 0.3 - 0.1 l.8ll) 0.8(1) <br />BLM 6/08/2001 0.66 1.6-0.3 1.3 0.6 <br />BLM 6/08/2001 0.94 2.3 - 0.4 2.0 1.8 <br /> <br />BLM - Bureau of Land Management DOW - Division of Wildlife <br />(I) Predicted flow outside of the accuracy range of Manning's Equation. ? = Criteria never met in R2CROSS Staging Table. <br /> <br />- 3 - <br />