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.. OO~6"O 1- U "~) Average Lower Basin Use Average Storage in Lake Mead Average Evaporation loss from Lake Mead Average Storage in Lake Powell Average Evaporation loss from Lake Powell COMPARISON OF EFFECTS Comparisons of the effects of the three scenarios are presented in the attached graphs. The three scenarios include: No Surplus being allowed. A 1996 sUrplus, A 1996 surplus, plus 10 additional years of surplus. As shown in Figure 1, a 1996 surplus determination would cause no significant effect to the annual probability of a shortage. With 1 0 additional years of surplus the earliest probability of shortage is generally advanced five years from 2030 to 2025 with a remote probability of a single occurrence in year 2014. The 10-year additional surplus generally increases the possibility of shortage by about 3 percent from years 2028 to 2036. There is little detectable effect prior to year 2023 and after year 2038. As shown in Figure 2, under average hydrologic scenarios lower basin shortages (1) are not affected by a 1996 surplus and (2) increase by about 30,000 acre-feet during the years 20~9 through 2036 from the lO-year additional surplus. As shown in Figure 3, the lO-year additional surplus reduces the probability of a flood control release from now through the year 2010 by an average of about 10 percent. The average amount of flood release that is conserved and put to use is shown on Figure 4. The volume conserved averages about 350,000 acre feet from now through about year 2015. This lingering flood conservation potential is to a large part related to the present condition of the reservoirs being near full. The storage capacities of the Colorado River reservoirs are such that full reservoir conditions may cause lingering effects 10 to 20 years into the future. Other figures also attached include: Figure 5 Figure 6 Figure 7 Figure 8 Average Lake Powell Elevation Average Lake Powell Contents Average Lake Mead Elevation Average Lake Mead Contents