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I i l I . , . I I I I stream. The CWCB study was used as the basis of this report and is summarized in Table 1. The CWCB data used to generate Table 1 is included in Appendix A. The CWCB has a minimum instream flow water right of35 cfs during the summer period (May 1 to September 30) and 15 cfs during the winter period (October 1 to April 30). Water availability studies conducted by the CWCB and WWE determined that, at certain times of the year, the CWCB' s instream flow rights do not reflect the flows naturally present in Trout Creek. The natural flow conditions can'be substantially less. Table 1 shows that the flow levels in Trout Creek are less than CWCB instream flow rights during August tIrrough March. In response to this infoffilation, WWE did additional streamflow measurements and flow modeling, and ABC conducted additional research to determine what minimum flow would constitute a threshold value for maintaining the integrity of the aquatic ecosystem in Trout Creek. 3.0 LOW FLOW MODELING WWE performed additional streamflow measurements on February 8, 2000 in order to provide a more refined analysis of Trout Creek and Caster Ditch under low flow conditions. This . additional work was done to satisfy CWCB staff concerns about modeling at low flows using Mannings coefficients developed at higher flows, and to more accurately model conditions in Caster Ditch. Trout Creek Trout Creek was gaged at a new station (Station 4) that was free ofice on February 8, 2000. The 'location of this station is shown in Figure 2. The flow measured in the creek on this date was " ,. 15.24 cfs. This measurement was used to develop a new, low flow Mannings'coefficient of 0,035. Model information for Statio114 is included in Appendix B. The new Mannings coefficient was used to re-model flows at Station 2, which was similar in characteristics, since that station was part of the basis for tile Bioassessment. Model information for Station is 2 included in Appendix C. \ 2