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<br />Chapter I Purpose and Need 6 <br /> <br />the facility's operation. A monitoring and adaptive management program is included in the <br />proposed temperature control alternative. <br /> <br />PREVIOUS AND RELATED EXPERIENCES <br /> <br />Glen Canyon Dam Outflow Temperature Control Study - This study conducted by <br />Reclamation (Ferrari 1987) presents an analysis of raising the water release temperatures <br />below Glen Canyon Dam by modifying dam penstocks with multi-level intakes. Predicted <br />temperatures of waters drawn from Lake Powell were calculated with a computer model. <br />The temperature change of this warmer water as it moves downstream was evaluated using <br />both a computer-generated temperature function and a simplified graphical method. The <br />study concluded that multi-level intakes could increase river temperatures by up to 18 OF <br />(Iooe), depending upon the time of year. <br /> <br />Flaming Gorge Outflow Temperature Control - The retrofit of Flaming Gorge Dam with <br />temperature controls provides the nearest parallel to the proposed temperature modifications <br />at Glen Canyon Dam. Much like Glen Canyon Dam, Flaming Gorge Dam was originally <br />constructed with deep intakes for the power penstocks. The deep intakes released extremely <br />cold water and these cold-water releases limited growth rates in the native and non-native <br />fisheries. Reclamation used the authority of Section 8 of the CRSP Act to retrofit the dam <br />with a series of shutter gates to improve temperatures for trout below the dam. <br /> <br />Mark Vinson, Director of the Bureau of Land Management's (BLM) National Aquatic <br />Monitoring Center has compiled all the available macroinvertebrate data for the Green River <br />below Flaming Gorge under a contract with Reclamation. Vinson found that overall there <br />have been some shifts in species composition that tend to have favored the amphipods or <br />scuds, but little or no change in total abundance of invertebrates and relatively little change in <br />the total taxa diversity or richness at the most upstream sites. <br /> <br />Post-project monitoring shows that the temperature control modifications have been <br />extremely effective at warming the water and producing results. The intakes at Flaming <br />Gorge Dam are set to release temperatures of approximately 13.50C during the summer. <br />Downstream areas experience some fairly significant warming toward ambient conditions. <br />For example, spring/summer temperatures in 1994 in upper Browns Park ranged between <br />approximately 140C to 180C, between approximately 150C to 200C in lower Browns Park, <br />and were slightly warmer in Lodore Canyon, approaching 21 oC. <br /> <br />The warming of the summer release temperatures from approximately 40C to 13.5 oc had an <br />immediate beneficial effect on trout growth and production in the tailwaters. Annual growth <br />of young trout increased from around 45mm to 150mm during the years immediately <br />following warming. Monthly summer growth of trout fingerlings also increased dramatically <br />with increased temperatures. <br /> <br />Below the immediate tailwater area, several native and non-native fish species appeared to <br />react quickly to the temperature increases. Several species, such as adult red shiners and sand <br />