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<br /> <br />Shortages in water releases for power production and energy use were <br /> <br />indicated by the computer simulation study in the December 1935 and November <br /> <br />1977 to February 1978 periods. These periods followed the extreme drought years <br /> <br /> <br />of 1934 and 1977. In the event that a repeat of these type years occurs in the <br /> <br /> <br />future, provisions for alleviating the shortages to energy use would be made by <br /> <br />a shut-down of the power plant for a short time period. The shut-down to alleviate <br /> <br /> <br />the shortage of 2,817 acre-feet in December 1935 and still maintain a 25 cfs <br /> <br /> <br />minimum release for downstream energy use (Tosco) and a 50 cfs bypass at the <br /> <br /> <br />Indian diversion would last for 7 days. The shut-down to alleviate shortages of <br /> <br /> <br />4,411 A.F. in November 1977, 8,761 A.F. in December 1977, 3,415 A.F. in January <br /> <br /> <br />1978, and 3,296 A.F. in February 1978 would last for 52 days. <br /> <br />If Colorado White River water resource development does not occur as <br /> <br /> <br />assumed in the simulation study (50,000 A.F. active capacity reservoir, 24,000 <br /> <br /> <br />acre-feet for irrigation and 30,000 acre-feet for oil shale development) then <br /> <br /> <br />there would be no energy use shortages or power plant shut-downs at Utah's White <br /> <br /> <br />River powerplant for the period of study. <br /> <br />B. Flood Routing <br /> <br />The proposed White River Reservoir was assumed full at the beginning of <br /> <br /> <br />the flood inflow. The service spillway will reduce the maximum 10-year flood <br /> <br /> <br />inflow by 1,000 cfs. The 100-year flood will be reduced by 1,100 cfs. The <br /> <br /> <br />service spillway will completely handle a 25-year frequency flood of 6,800 cfs. <br /> <br /> <br />The reservoir will reduce the probable maximum flood with a peak of 17,500 cfs <br /> <br />to 15,490 cfs or a total of 2,010 cfs. The flood peaks are not reduced any more <br /> <br /> <br />than this due to the 4 to 6 day base length of these large flood hydrographs <br /> <br /> <br />and the resulting large volume of water contained in them. Because of the <br /> <br /> <br />relatively low routing effects of the reservoir on these large floods, the combined <br /> <br /> <br />spillways for the dam will be designed to handle up to 15,500 cfs. Design for <br /> <br /> <br />this capacity will be based on adequate factors of safety and freeboard allowances. <br /> <br /> <br />A flood of this magnitude is more than twice that which has been recorded in the <br /> <br /> <br />past 50 years on the White River. The recurrence interval of this highly unlikely <br /> <br /> <br />hydrologic event is estimated to be 10,000 years. <br /> <br />C. Hinimum Release Rate Below White River Dam <br /> <br />A minimum reservoir release rate of 250 cfs below the dam is proposed. <br /> <br /> <br />If the past 50 years of records is indicative of the future then this flow could <br /> <br />- 38 - <br />