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<br />001441 <br /> <br />-9- <br /> <br />'. <br /> <br />extent. Colorado says that data for drouth conditions. and sub-normal cy- <br />cles such as 1931-1940. are important. but says that such dota should ap- <br />pear separutely from virgin flow estimations. Due to the uncertainties as <br />to when allOtlYilr such cycle of years may be enoountered. and as to what then <br />may be the status of development. Colorado says that so-called virgin flows <br />for such an assumed drouth cycle will be misleading, and will not indioate <br />the streamflov<s available for irrigation, power, and other purposes, unless <br />accompanied by reservoir operation studies to show the effeots of stream- <br />flow regulation and the additional supplies of water thereby made available <br />during suoh a period of years. Colorado suggests the inolusion in the Re- <br />port of suoh reservoir operation studies on virgin flow oonditions to show <br />the regulating effeot at Lee Ferry and the International Boundary of mass <br />operations of reservoirs above those points. <br /> <br />20. Virgin flow quanti ties shown in the Report are the sum of, (a) <br />the average annual streamflows recorded at (or oaloulated for) the desig- <br />nated gaging station; plus (b) the e.llowances for upstream "depletions" <br />in the average year of the same period, - said "depletions" being the quan- <br />tities of water estimated to have been withheld from the stream by the di- <br />version, use and storage of water from and in the natural drainage basin <br />upstream from the designated station. Neither the reoorded streamflows nor <br />the "depletion" allowanoes of the historic period. are shown in the Report. <br />Colorado suggests that, for two key stations, the Report should contain <br />detailed information concerning both items; and that the key stations should <br />bel Colorado River at Lee Ferry and International Boundary. <br /> <br />.. <br /> <br />.. <br /> <br />21. Colorado points out that since "depletions" are a part of the es. <br />timated "virgin 1'lows," an understanding 01' what is meant by "virgin 1'10v<s" <br />depends in part on the meaning 01' "depletions," whioh are defined in <br />general as the di1'ferences between diversions and returns; and that evapo- <br />ration losses from existing and potential main,.stem reservo,irs are entered <br />as depletions, but are not measurable by the di1'ference between diversions <br />and returns. A proper definition of "depletions" would include bath the <br />manner of calculation, or the factors employed in the estimations, and the <br />place of evaluation, ,met her at tre places where such "depletions" occur, <br />or in terms of their resulting effects at points downstream. The data <br />presented are inconsistent in this respect, and there1'ore are not direct- <br />ly comparable. Upper Basin depletions appear to have been evaluated as 01' <br />the places where they ocour, ,mereas in the Boulder and Gila divisicns 01' <br />the Lo""r Basin, the upstream "depletions" appear to have been credited <br />with the estimated salvage of water or reductions in natural conveyanoe <br />losses att['ibutable to the diminished volumes and regulated character 01' <br />the 1'lows resulting from upstream development. Colorado urges that both <br />basins be treated alike. <br /> <br />( <br />f}' <br />~' ., <br /> <br />11 <br />.,...,,~ <br /> <br />22. The recorded streamflows at designated gaging stations are the <br />unconsumed out1'lows from the upstream drainage basin, that v.ere not with- <br />held 1'rom the stream either by man-made "depletions" or by natural losses <br />01' water. In calculating the "virgin nows" of the Report, the man-made <br />"depletions" ""re added to the recorded out 1'1 ows , and the natural losses <br />were ignored. Thus "virgin flows" may be said to indicate the stremnf'lows <br />that might have been recorded during the average year 01' a similar climatic <br />