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I I I I I I I I I I I I I I I I I I I For the administration of the Keesee account, it is more convenient to express these unit responses as a function of diversions occurring during the current month and during all previous months. Table II summarizes average monthly diversions, return flows, depletions, and consumptive use as calculated in Volume I of this report. Also tabulated are consumptive use and irrigation returns expressed as a percentage of average monthly diversions. In August, for example, 70% of the amount diverted is consumed by the crop during the month, and the remaining 30% returns to the aquifer. The pattern of that return to the stream is described by the percentages indicated in the table above. The Short-term Return Flow Factors are calculated by multiplying the monthly irrigation return, expressed as a percent of diversions, by the percent accretion for a particular month. Long-term return flows are a function of operations of the ditch system in prior years. In April, for example, 48.8% of the amount diverted becomes an irrigation return. Of that amount, 21.6% will return to the river during April, based on the unit responses tabulated above. This means that for the average year, 49.0 acre-feet of 464.6 acre-feet diverted will return during April. Yet the average return flow to the river during April has been shown to be 137.8 acre-feet, as shown in Table II. The difference between the total return of 137.8 af and the short-term return of 49.0 af is the long-term or residual return flow. ~~~.!"I11_~etur~I~I','.XI!ce.t()J"s_.ll.re these residuaJ return flows expressed as _-a-percent~ge__QJ_a veJ:agll.-._'illlJllIter. _.cli"er-&ioll&..-during_JilELP'rECEO~dinK_~~,-- (ShJl.rt-term .Return Flow Factors, by contrast, are expressed as a percentage -'~- ,.---- ~ - - - ,- - ." . .- - . -. . -- -- -....._--- -,.~-,- --. _._--'---~,."._~._,._._~~,.,_.<----"._-~~--_..~"...._."-. of average monthly diversions during the current year.) The net effect of winter operations has resulted in a gain to the river of 114 acre-feet, or 2.58% of average summer diversions. As more fully described below, Winter Season Return Flows will be returned simultaneously with Short-term and Long-term obligations. Winter Season Return Flow Factors are total winter returns expressed as a percentage of average summer diversions, distributed over the entire summer season. All Return Flow Factors are summarized in Figure 2, which is a model accounting form. The use of Figure 2 is more fully described in the following section. -8-