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<br />tat ion to reduce it to the equivalent precipitation at 3,600 feet. The <br />equivalent precipitation for all stations was then totaled and divided by <br />the number of stations on a monthly basis. <br />Table 6 was adapted from the report by R. A. Schleusener 8/. <br /> <br />TABLE 7 <br />Effective Precipitation in Inches <br /> <br />Month Jan Feb Mar April May June July Aug Sept Oct Nov Dec <br />.6 .6 .8 .8 .8 .8 1.0 1.0 1.0 .8 .8 .8 <br /> <br />The precipitation up to the limit shown in Table 7 was multiplied by the <br />remaining area. This is shown as column 5 in Table 8. The remaining area <br />is the total area of the reservoir for the month minus the total of the <br />water surface area, the streamside area, and the terrace area. From these <br />computations it was determined that about 95 percent of the precipitation <br />on the reservoir area would have evaporated and transpired. <br /> <br />RESULTS <br /> <br />Table 8 shows the computed monthly evaporation for each of the four parts <br />and the resulting net evaporation for the periOd January 1965 through May <br />1979. <br /> <br />Table 9 shows the net annual evaporation, as described under PROCEDURE, <br />which has previously been used on a preliminary basis, compared to the <br />net annual evaporation computed from this study (Table 8). The net eva- <br />poration is less under this study when the reservoir is low but greater <br />when the reservoir is high. The average evaporation under this study is 5 <br />percent higher than the preliminary figures. This is mostly due to the 3 <br />percent higher gross evaporation rate of 68.3 inches per year compared to <br />66.2 inches from the former estimates. <br /> <br />RECOMMENDA T1 ONS <br /> <br />It is recommended that the results of this study be used to make a water <br />budget analysis for Lake Powell. This will improve the estimate of the <br />amount of water stored in the banks. It might also help to determine the <br />amount of bank storage that is recoverable. <br /> <br />It is also recommeneded that the results of this study be used to determine <br />a simpler method of estimating evaporation. A method that could be used in <br />operations would be beneficial. One method that should be considered is to <br />use pan evaporation at Wahweap. <br /> <br />20 <br />