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The spring /summer flow of 325 cfs was reduced to 170 cfs for the June 15 through July 31 time <br />period because of water availability concerns. The instream flow recommendation of 170 cfs <br />was derived to maximize the existing bluehead and flannelmouth sucker habitat available under a <br />declining hydrograph, by maintaining an average depth of 1.0 foot over the measured riffle <br />cross - section. An average depth of 1.0 foot combined with average velocities exceeding 1.3 <br />fl/sec, were determined to be marginally suitable bluehead sucker habitat (see Anderson & <br />Stewart Report). <br />Because the PHABSIM / RHABSIM data only quantified suitable versus unsuitable hydraulic <br />habitat as a function of discharge, the CDOW and the BLM staff used the results of the <br />R2CROSS Method to develop the fall /winter instream flow recommendation of 115 cfs. The <br />112CROSS Method suggests that fall /winter flows should maintain at least 2 of 3 of the identified <br />critical hydraulic criteria. At the Cross Section 41 site, 115 cfs meets 2 of 3 criteria (average <br />depth and velocity) by providing on average, 0.8 feet of depth and velocities well over 1.0 ft/sec. <br />The fall /winter flow recommendation was further reduced to 80 cfs, for the time period of <br />September through February, due to water availability concerns. It should be noted however, <br />that 80 cfs still maintains adequate velocity (approximately 2.5 ft/sec), a wetted perimeter of <br />almost 60% and an average depth of nearly 0.7 feet. <br />