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<br />Draft - Do Not Cite <br /> <br />29 <br /> <br />00Q353 <br /> <br />August 2003 <br /> <br />---. <br /> <br />3.4 HABITAT MAINTENANCE THRESHOLDS <br /> <br />The following sections presents exceedances for flow thresholds considered important for <br />maintenance of endangered fish habitats in the lower Gunnison River under the six flow <br />scenarios 'consideredin this report. Thresholds evaluated and their basis are discussed in <br />Section 2.4. <br /> <br />3.4.1 FWS Flow Recommendations <br /> <br />As presented in Section 2.4.1, FWS flow recommendations consisted of a <br />recommendation of the long-term annual mean munber of days that flow should exceed half- <br />bankfull (8,070 cfs) and b~ flow thresholds (14,350 cfs) each year as well as instantaneous <br />peak flow recommendations in different hyc;lrologic conditions. Recommendations were made <br />for flows in the Gunnison River as measured at "the Grand Junction gage. Each of the six flow <br />scenarios were evaluated to determine how well they met these FWS recommendations. <br /> <br />3.4.1.1 FWS Half-Bankfull and Banldull Recommendations <br /> <br />The number of days per year that flows would exceed half-bankfull conditions (8,070 cfs) <br />at the Grand Junction gage are presented in Table 9 for the six flow scenarios. The long-term <br />means for the periods 1975 through 2000 and 1978 through 1997 are also presented to allow <br />comparison with the FWS flow recommendations (as presented in Table 2). <br /> <br />For dry years (e.g., 1989), none of the flow scenarios would produce flows that exceed <br />the half-bankfull condition. Historically, half-bankfull flows were exceeded from 0 to 74 days. <br />For a very wet year {1984), Western C, Western D, and the Reclamation scenarips exceed the <br />gage flows by 8 days (about 14%). For the 26-year period of record, the Reclamation scenario <br />would have more total days in which flows exceeded half-bankfull conditions (468 days versus <br />420, 445, 452, 439, and 446 days for gage flows, and Western A, Western B, Western C, and <br />