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<br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />During the BO-day period, there were 21 days when natural flows reaching the <br />upper gage were in excess of 900 cfs thus precluding the need for supplemental <br />releases. There were 59 days when supplemental releases from Ruedi provided <br />needed water to the IS-Mile Reach. ,With the releases, the 700 cfs minimum was <br />met at the upper gage 37.3 percent of the 59 days compared to 15.3 percent if the <br />releases had not been made. Water year 1991 is considered a below normal water <br />year and the 600 cfs minimum for dry years was met 74.6 percent of the 59 days <br />compared to 30.5 percent if the releases had not been made. The Ruedi releases <br />significantly increased the number of days when flows fell within the range for <br />providing high quality Colorado squawfish habitat in the IS-Mile Reach. <br /> <br />During the period when flows were low (i.e., below the recommended flow), the <br />supplemental Ruedi releases also had a beneficial effect on habitat conditions <br />in the IS-Mile Reach. For instance, a release of 190 cfs on October 15 resulted <br />in a flow at the top of the IS-Mile Reach of 570 cfs; without the release the <br />flow would have been an estimated 393 cfs. Thus, the supplemental release <br />resulted in a 45 percent increase in flow during a time when available habitat <br />would have otherwise been limited. During the 59 days when flows would otherwise <br />have been below 900 cfs, Ruedi releases resulted in an average daily flow <br />increase of 26 percent at the Palisade gage. Table 2. displays the relative <br />amounts of habitat available at various flows, and demonstrates that significant <br />increases in habitat resulted from the availability of the supplemental releases. <br /> <br />Conclusions <br /> <br />Endangered fish releases from Ruedi Reservoir have proven to be an effective <br />means for augmenting flows in the IS-Mile Reach during the critical summer <br />months. Improved planning and monitoring would result in an even more effective <br />use of available Ruedi water. During 1991, there were IB days in which water was <br />released when flows were in excess of the recommendations. This resulted in the <br />loss of 3,B7S ac ft that could have been used when additional water would have <br />been more beneficial. While it is not possible to anticipate natural events such <br />as rainstorms, the number of days in which excess flows occur could be reduced <br />by closer monitoring. <br /> <br />The release scheduling problem was compounded by not knowing much water would be <br />available for supplemental flows. At the beginning of August 1991, only <br />10,000 ac ft of water were available for endangered fish releases. This resulted <br />in rationing the 10,000 ac ft so that water would be available until October 31. <br />If there had been earlier approval the full 20,000 ac ft, higher releases could <br />have been made in late August and early September when flows in the IS-Mile Reach <br />were in greatest need of augmentation. <br /> <br />Response of the IS-Mile Reach population of Colorado squawfish to improved <br />habitat conditions will be difficult to assess until targeted flow regimes can <br />be met for an extended number of consecutive years. Improved habitat should, <br />over time, translate to a higher carrying capacity for this stretch of river <br />resulting in an increase in population size, assuming that proper flow and <br />habitat conditions are met during the other months of the year. At present, the <br />IS-Mile Reach remains an important stretch of river for the Colorado squawfish. <br />During spring 1991, a total of 23 adults were captured and released there; on a <br /> <br />4 <br />