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<br />APPENDIX D <br /> <br />Potential Benefits Associated With the Release of 3.000 Acre-Feet <br />of Water DurinQ Julv 15 throuQh October 15 <br />in the IS-Mile Reach of the Colorado River <br /> <br />Kaeding and Osmundson (1989) recommended a flow window of 700-1200 ft3/s during <br />July, August, and September for the maintenance and enhancement of Colorado <br />sQuawfish habitats in the 15-mile reach. They further indicated that 600 ft3/s <br />would be an adequate short-term lower limit during dry years. <br /> <br />A primary objective toward recovery and delisting of Colorado sQuawfish <br />identified in Kaeding and Osmundson (1989) is a flow-habitat management <br />scenario for July, August, and September that would maintain 95 percent or more <br />of the aggregate run, pool, and riffle habitat in the 15-mile reach. The <br />700-1200 ft3/s flow window will achieve the desired flow-habitat relationship <br />that would aid recovery. <br /> <br />Table 1 presents monthly discharges that would have occurred in the IS-mile <br />reach for the period of record 1962-1982 under present conditions and with the <br />project. When comparing monthly discharges with the flow window recommended <br />for the 15-mile reach, it becomes apparent that there are numerous occasions <br />when the minimuaof 700 ft3/s is not met, particularly in August, September, <br />and October: thus, there is a need to augment flows in the 15-mile reach if we <br />are to achieve the desired flow-habitat relationships that would aid recovery. <br />Assuming Muddy Creek were operating, it can be seen that for the 21-year period <br />of record, the minimum for July was exceeded in all but 2 years. In August, <br />the minimum would not be met in 9 out of 21 years. In September, it would not <br />be met in 16 out of 21 years, and in October, it would not be met in 6 out of <br />21 years. <br /> <br />In a recent operational summary prepared by Muddy Creek project proponents, it <br />was indicated that, for the hydrologic period of analysis (1962-1982), that <br />releases to enhance rare fish habitat could have been made in 15 out of 21 <br />years. Figure 1, a graph from the operational summary, illustrates the years <br />and amount (3,000 acre-feet) of water available for delivery to the IS-mile <br />reach. <br /> <br />Table 2 illustrates post project flows with the full 3,000 acre-feet, which <br />equals about 50 ft3/s for 30 days, delivered in September. This is but one of <br />many possible scenarios for use of the 3,000 acre-feet of water from the Muddy <br />Creek. Project. Augmentation of post-project flows of this magnitUde will <br />effectively reduce the number of months when the 700 ft3/s minimum is not met, <br />as well as improve fiow conditions in other months when the minimum cannot be <br />met. Referring to Table 1 again, it can be seen that releases of 3,000 <br />