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<br />~; r_ :: ~~ ~ t <br /> <br />The responses indicate that 86 percent of the <br />operations were considered an unqualified success <br />in solving or at least improving the problem <br />situation. Although none of the destratification was <br />done for evaporation suppression reasons, at least <br />one of the utility managers recognized that the <br />water surface temperature was decreased and <br />staled that suppression was probably a side benefit <br />of the operation. <br /> <br />Destratlflcatloo ror eovlroomeotal <br />reasons <br /> <br />One of the problems related to deep reservoirs <br />is the extremely cold flow from below thermocline <br />outlels which may be significantly colder than the <br />nalural river flow. An example of this is the Green <br />River below Flaming Gorge Dam. Since construc- <br />tion of this dam, the reservoir outflow has been <br />about 460F compared to 550F natural temperature. <br />This has caused a dramatic decrease in the <br />reproduction rate of some native species of fish in <br />the area. Because of the concern of the Fish and <br />Wildlife Service over these endangered species, the <br />USBR made an attempt in 1972 to destratify a <br />small portion of the impoundment close to the <br />outlet. No report has been published concerning <br />this operation, but internal USBR correspondence <br />describes the operation as follows (USBR Letter, <br />1973): <br /> <br />Two 25 HP compressors (194 dm at 125 psi) were <br />used in this pilot project to inject air through existing <br />conduits in the dam and outlet structure. The <br />operation produced no effect on outflow temperature <br />ber3use "the efficiency of this year's pilot system was. <br />st'Yf'rc]y limiled by its size and location," The <br />operation was apparently below a critical limit of <br />enerl{Y input which resulled in a negligible destrati. <br />(i('alion effet'1. <br /> <br />The correspondence suggest that in order to <br />destratify the main downstream basin at Flaming <br />Gorge to the required depth, 320 HP would be <br />required. and that anything less than this scale of <br />operation would be inconclusive (the pilot study <br />had envisioned mixing of only a section within 500 <br />feet of the dam). <br /> <br />Reservoir eoergy budget <br /> <br />The U.S. Geological Survey has published <br />several Professional Papers which deal with <br />computing various components of the energy <br />budget of reservoirs including one concerned with <br />the effect on temperature and evaporation of added <br />heal from a powerplant (Harbeck et aI., 1959). In <br />developing a model 10 simulale the effect of <br />thermal mixing on surface temperature. t.he <br />changes in energy parameters are of great <br />importance. These USGS papers will be discussed <br />later in connection with the energy budget <br />calculations, <br /> <br />7 <br />