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Draft - Do Not Cite 31 OOJ355 August 2003 Western D, respectively). The mean number of days in which half-bankfull flows would be exceeded for the period 1978 through 1997 (the period that served as the basis for the recommendations presented in Table 2) under the Western and Reclamation scenario are all greater than the FWS recommended mean value of 20 days per year for the same time period. Half-bankfull flows would be exceeded about every 2 years for each of the scenarios (12 to 13 years out of26 years). The number of days per year that flows would exceed bankfull conditions (14,350 cfs) at the Grand Junction gage are presented in Table 10 for the six flow scenarios. The long-term means for the periods 1975 through 2000 and 1978 through 1997 are also presented to allow comparison with the FWS flow recommendations (as pr~ented in Table 2). All Western scenarios would result in more days above bankfull flow than either the gage or Reclamation scenarios. For the period 1978 through 1997 (the period that served as the basis for the recommendations presented in Table 2), all of the Western scenarios would exceed the 4-day recommended mean above bankfull flow. The Reclamation scenario would approximate that recommendation but fall somewhat short (3.9 day/year mean). The return period for bankfull flows under the Western scenarios would be shorter than either the gage or Reclamation scenarios. (range 2.6 to 4.3 years for Western scenarios; 5.2 and 6.5 years for gage and Reclamation scenarios). 3.4.1.2 FWS Instantaneous Peak Flow Recommendations Figure 17 shows the percent of years that FWS targets for instantaneous peak flow at the Grand Junction gage would be achieved under the six scenarios evaluated. These values are very similar for all scenarios for targets at half-bankfull flow (8,070) or below. For higher instantaneous peak flows, the Western scenarios (especially Western C and D) would tend to achieve these targets more frequently.