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<br />000968 <br /> <br />Iii <br /> <br />The total precipitation which falls on the contiguous United States <br />amounts to 4.2 trillion gallons. each day or 4. 75 billion acre-feet <br />per year. This represents only about one-tenth of the total water <br /> <br />vapor which passes overhead in the atmosphere, a tremendous <br /> <br />water reservoir which may be tapped through the application of <br /> <br />weather modification techniques. <br /> <br />The National Academy of Science reported recently that a critical <br /> <br /> <br />review of cOJ;nmercial cloud' seeding project statistics revealed <br /> <br />precipitation increases of 10 to 20 percent. If the larger percentage <br /> <br /> <br />flowing across the United States as vapor in the atmosphere. <br /> <br />1n- <br /> <br />"~N'''''; <br />~:... ~~ ~.;t?- <br />~ ~ ,>>K- <br /> <br />I <br /> <br />t"-"-~. <br />~;k'i <br />*~..:.-;,r~~.~.-..;~ <br />~~$~r f'Q <br />,.1't!i'''' ,,' <br />^,.. """",~,,; <br />x''''' ;.:-;':J!i;~ <br /> <br /> <br /> <br /> <br /> <br /> <br />:., $' <br />~i~. ~g~~ <br />~'~M-":'-:--'~ <br /> <br /> <br />I <br /> <br />of increase is applied to the annual precipitation over the United <br /> <br />States, the annual yield is nearly a billion acre-feet of additional <br /> <br />water., almost a trillion gallons a day. <br /> <br />This impressive increase <br /> <br />is still only a fraction, about 2 pe,rcent, of the total volume of water <br /> <br />creased research and scientific experimentation will undoubtedly <br /> <br />provide more efficient techniques that will enable us to tap greater <br /> <br />percentages of this vast reServoir'of atmospheric water where and <br /> <br />when additional supplies are needed for beneficial uses. <br /> <br />The above figures demonstrate that nature is not a very efficient <br /> <br />rainmaker. <br /> <br />By improving somewhat on nature's efficiency, man's <br /> <br />efforts would have a scarcely measurable effect on the total mois- <br /> <br />ture in the atmosphere. <br /> <br />A precipitation modification program con- <br /> <br />ducted in one locality would not significantly reduce the water content <br /> <br />27 <br />