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. feet. From Table 5 the annual average evaporation for a consecutive five- year sequence may be as high as 3275 acre-feet for the same probability level. Using Tables :: i hrough 5 coupled with the policy decision by the con- tracting parties r >rding the safety level of the full satisfaction of the requirements, ., target replacement requirement can be determined. A reasonable assumption appears to be one that would meet the replacement requirement presented by a five-consecutive-years'-high evaporation event at the 0.05 probability level. The assumption of an average reservoir content that would require 3255 acre-feet annual replacement (Table 5) is however on the high side, because of the limited likelihood of the pool's content to be average under such a stress situation. It is more likely that the content ,will be below the 22,000 acre-feet value with an annual evaporation loss of 3200 acre-feet or less. Annual variations within the five years will be provided for by carry-over storage from one year to the next. Assuming that the above considerations are acceptable to the contracting parties in Table 6, replacement volumes are shown that will have to be pro- vided for from emergency sources which will be discussed later in this report. Table 6. Annual Excess Replacement Requirement in Acre-Feet for an Annual Replacement Input of 3250 A~re-Feet Once in every Deficit in ac-ft for 0 5 10 20 100 --years-- (a) Single year none none 65 270 470 (b) Three consecutive years -- none none 55 175 (c) Five consecutive years -- none none none 25 To determine the most desirable target replacement requirement for this contract, prior to the use of Tables 3, 4 and 5 a policy decision must be made. The quoted tables show the expected replacement quantities for single-and multiple-year events at different probability levels. At this - 8 - M. W. BITTINGER AND ASSOCIATES. INC.