BOARD01130 - Laserfiche WebLink

Home Browse Search

, - e e Instream Flow Recommendation(s) I BLM's flow recommendation is for 5.1 cfs (April I - June 30). 1.7 cfs (July I to July 31) & 1.0 cfs (August I - March 31) (see BLM Letter in Appendix A). land Status Review Total Length Land Ownership Upper Terminus Lower Terminus (miles) % Private % Public Raspberry Creek Trapper Creek 2.7 0% 100% This segment is located on 100% public land managed by the BLM (See attached Figure I). Biological Data The BLM has conducted field surveys of the fishery resources on this stream and have found a natural environment that can be preserved. As reported for this reach of stream in their September 24, 1999, letter to the CWCB and enclosed fishery surveys (see Fish Survey in Appendix B), "Fishery Surveys indicate that the stream environment is in stable condition and supports a self-sustaining Colorado River cutthroat trout fishery. Spawning substrate and food availability are good for salmonids. However, cover and pools are limited, underscoring the importance of adequate flows to maintain sufficiently cool stream temperatures during the summer and fall high temperature period." Field Survey Data BLM and CWCB staff used 1he 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 type that would dry up first should the 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 the field data collected in regards to this proposed segment. Biological Flow Recommendations The CWCB staff relied upon the biological expertise of the cooperating agencies to interpret the output from the R2CROSS data collected to develop the initial, biologic ins1ream 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 parame1ers, average depth, percent wetted perimeter and average velocity are used to develop biologic instream flow recommenda1ions. The CDOW has determined that by 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 collec1ed with the results shown in Table I below. Table I 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 predicted flows based on Manning's Equation (240% and 40% of Q), the summer flow recommendation based upon meeting 3 of 3 hydraulic criteria and the winter flow recommendation based upon 2 of 3 hydraulic criteria.