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CDOW and BLM were concerned that the standard R2CROSS method may not be appropriate for this reach of the San Miguel River due to its major width (over 75' wide in most places), type of fish species present (warm /cool water species) and its big river channel hydraulics and characteristics. Accordingly, BLM and CDOW staff compared results from their PHABSIM/RHABSIM data analysis with their R2CROSS analysis. Using the results from the PHABSIM/RHABSIM data analysis, the maximum amount of usable habitat for bluehead suckers was produced at a flow of 500 cfs and for flannelmouth suckers at a flow of 325 cfs. The R2CROSS analysis indicated that a spring /summer flow of approximately 650 cfs was necessary to meet all three of the critical hydraulic criteria at this site and a fall /winter flow of 115 cfs would meet 2 of 3 of the hydraulic criteria. CDOW and BLM are recommending that a flow of 325 cfs, for the time period of April 15 through June 14, is the minimum amount necessary to preserve the natural environment to a reasonable degree, for this reach of the San Miguel River. This is based on the assumption that 325 cfs would preserve 90% of the weighted useable area available to the bluehead sucker and 100% of the weighted useable area available to the flannelmouth sucker. BLM and CDOW staff also believe a flow that maintains adequate bluehead and flannelmouth sucker habitat should also maintain adequate roundtail chub habitat. The spring /summer flow of 325 cfs was reduced to 170 cfs for the June 15 through July 31 time period because of water availability concerns. The instream flow recommendation of 170 cfs was derived to maximize the existing bluehead and flannelmouth sucker habitat available under a declining hydrograph, by maintaining an average depth of 1.0 foot over the measured riffle cross - section. An average depth of 1.0 foot combined with average velocities exceeding 1.3 ft/sec, were determined to be marginally suitable bluehead sucker habitat (see Anderson & Stewart Report — Appendix F). Because the PHABSIM/RHABSIM data only quantified suitable versus unsuitable hydraulic habitat as a function of discharge, CDOW and BLM staff used the results of the R2CROSS Method to develop the fall /winter instream flow recommendation of 115 cfs. The R2CROSS Method suggests that fall /winter flows should maintain at least 2 of 3 of the identified critical hydraulic criteria. At the Cross Section #1 site, 115 cfs meets 2 of 3 criteria (average depth and velocity) by providing on average, 0.8 feet of depth and velocities well over 1.0 ft/sec. The fall /winter flow recommendation was further reduced to 80 cfs, for the time period of September through February, due to water availability concerns. It should be noted however, that 80 cfs still maintains adequate velocity (approximately 2.5 ft/sec), a wetted perimeter of almost 60% and an average depth of nearly 0.7 feet. M