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<br />ODfi400 <br /> <br />-11- <br /> <br />(1) T1'.8 word "depleted" here refers to natural losses, since by <br />definition there v.ere no men-ma.de "depletions" under virgin conditions. <br />and miGht better read "reduced" or "diminished." <br /> <br />(2) A "growing stream" do,-m to the Black Canyon section does <br />not mean that natural losses are absent above that point. or may be ignor- <br />ed as in the Report. On the contrary it means only that inflows to the <br />muin river, or contributions from tributary streams and areas, are great- <br />er in amount than the quantities of water lost in conveyance. Similarly, <br />a losing river in the desert region does not mean that there were no <br />tributary contributions under virgin conditions, or that they may be dis- <br />regarded. Instead, it means that natural losses from the main-river <br />channels were greater in amount than the tributary inflows (except at <br />times of flood). <br /> <br />(3) Hith "virgin flows" of 2,282,000 acre-foet at Phoenix and <br />1,271,000 acre feet at Dome, the conveyance loss would be 1,011,000 acre <br />feet plus all the virgin tribul;ary inflow to the river section. <br /> <br />(4) The indicated net gain from Lee Ferry to Laguna Dam, ao- <br />cording to the above table, is 180,000 aore feet. Since the contribu- <br />tions reported from Little Colorado and Virgin Rivers together amount to <br />648.000 acre feet, the table implies that natural losses under virgin <br />conditions were 468,000 acre feet. ColoradO questions the accuracy of <br />the estima.tes for the two reported tributaries. and says that miscellane- <br />cUs tributary drainage areas vrere ignored. Under so-called virgin condi- <br />tions the tributary contributions between Lee ?erry and Laguna Dam (as <br />estimated by Colorado engineers) averaged 495.000 'tcre feet from the Little <br />Colorado River, 392,000 aore feet from the Virgin River, 413.000 acre feet <br />from miscellaneous drainages between Lee Ferry and Boulder Dam, and 200,000 <br />acre feet from miscellaneous streams (including Hilliams River) and areas <br />bet,~en Boulder Dam and laguna Dam. Assuming that total fiGure of 1,500,000 <br />acre feet, of t he net gain "between Lee Perry andLaguna Dam is 180,000 acre <br />feet, as shovlli in the above table. the natural conveyance loss would aver- <br />age 1,320,000 acre feet annually along that river seotion under virGin <br />conditions. <br /> <br />(5) From the instances above mentioned it is apparent that <br />natural conveyance losses in the Colorado River Basin involve substantial <br />quantities of water. and it seems self-evident that such losses under so- <br />called "virgin conditions," when streamflows were maximum and wholly un- <br />reGulated. would have been greater than those observed and calculc.ted <br />from records during tre historic period. ColoradO suggests that estimates <br />of natural losses should be made by the Bureau of Reclamation. and should <br />appear in the Report, covering so-called virgin conditions. or the condi- <br />tions of the period of record, or both. As estimated by ColoradO engi- <br />neers during the period 1908-1942 (when man-made depletions averaged <br />1.952.000 acre feet per year above Lee Ferry. and 2.911.000 aore feet be- <br />low Lee Perry, and when the reoorded flow at the International Boundary <br />averaged 12.683.000 acre feet annually), the natural conveyance losses <br />averaged 870,000 acre feet above Lee Ferry. and 2,640,000 aore feet below <br />Lee Ferry, or totalled 3,510,000 acre feet annually in the Colorado <br />