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00D398 -9- extent. Colorado says that data for drouth oonditions, and sub-normal cy- cles such as 1931-1940, are important, but says that such d"ta should ap- pear sepa~.tely from virgin flow estimations. Due to the uncertainties as to ,",hen anotrer such cycle of years may be encountered, and as to who.t then may be the sto.tus of development, Coloro.do says that so-co.lled virGin flows for such an assumed drouth oycle will be misleading, and will not indicate the streo.mflow available for irrigation, power, and otrer purposes. unless accompanied by reservoir opero.tion studies to show the effects of streo.rn- flow regulation and the additional supplies of water thereby made available durinG such a period of years. Colorado suggests the inclusion in tre Re- port of such reservoir operation studies on virgin flow conditions to show the regulating effect at Lee Ferry and the International Boundnry of mass operations of reservoirs above those points. 20. Virgin flow quantities shown in the Report are the sum ofl (a) the average annual streamflows recorded at (or caloulated for) the desig- nated gaGinG station; plus (b) the allowances for upstream "depletions" in the average year of the same period, - said "depletions" beinG the quan- tities of water estimated to have been withheld from the stream by the di- version, use and storage of water from and in the natural drainage basin upstream from the designo.ted station. Neither the recorded stre~lows nor the "depletion" allov.wlces of the historic period, are shom in the lieport. Colorado suggests that, for two key stations, the rleport should contain detailed information concerning both items; and that the key stations should bel Colorado River at Lee Ferry and International Boundary. . 21. Coloro.do points out that sinoe "depletions" are a part of the es. timated "virgin flows," an understanding of what is meant by "virgin flows" depends in part on the meaning of "depletions," which are defined in general as the differences between diversions and returns; and tho.t evapo- ration losses from existing and potential main-stem reservoirs are entered as depletions. but are not l!l6asurab Ie by the difference betvleen diversions and returns. A proper definition of "depletions" would include bath the manner of calculation. or the factors employed in the estimations, and the place of evaluation, mether at tre places where such "depletions" occur, or in terms of their resultinG effects at points downstreo.m. The data presented are inconsistent in this respect, and therefore are not direct- ly cOI"par8ble. Upper Basin depletions appear to have been evaluated as of the plo.ces where they occur, whereas in the Boulder and Gila divisions of the Lamr Basin, the upstream "depletions" appear to have been credited with the estimated salvage of water or reduotions in ooturo.l oonveyo.noe losses attributable to the diminished volumes and regulated oharo.cter of the flows resulting from upstream development. Colorado urges tho.t both bo.sins be treated alike. 22. The reoorded strearnflows at designated baging stations are the unconsumed outflows from the upstream drainaGe basin, that v.ere not with- held from the stream either by man-made "depletions" or by naturo.l losses of water. In calculating the "virgin flows" of the Report, the man-made "depletions" were added to the recorded outflows. and the natural losses were ignored. Thus "virgin flows" may be said to indicate the stremnflows that might have been recorded during the average y'.ar of a similo.r climatic