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<br />1.""'-' rr":'~- <br />lL_,,;,,~~,,), <br /> <br />13 <br /> <br />Manner of Making The Studies <br /> <br />The customary method of moking river and reservoir oper- <br />otion studies is to operate potential reservoirs of various hypo- <br />thetical copocities uti lizing the woter supply occurring during the <br />adopted study period, it being assumed that the woter supply <br />thot occurred during such a period would repeot itself in the <br />future in the some chronological sequence, <br /> <br />The long drouth period which hod its initiation in 1931 in <br />the western part of the United States, and which may not yet be <br />ended, has disclosed weoknesses in the formerly accepted method <br />for making river and reservoir operation studies, Monyexamples <br />could be given to illustrote this, such as the increase in length of <br />the holdover period for the Colorado River storage project reser- <br />voirs as the drouth period extended beyond thot upon which the <br />original studies were predicated, The situation on the Upper Rio <br />Grande also illustrates this. Until 1950, using records of runoff <br />of Rio Grande beginning in 1890, it was not supposed that Ele- <br />phant Butte Reservoir (a key facility for the United Stotes Bureau <br />of Reclamation Rio Grande Project in New Mexico and Texas) <br />would ever become empty, However, it has been essentially dry <br />during the past several years, As a further illustrotion, the water <br />supply for Lake Meade on the Colorado River has not been as <br />much as estimated at the time the studies were made which <br />formed the basis for the authorization of that project, A more <br />recent example is the International Falcon Reservoir located on <br />the Lower Rio Grande which wos constructed by the combined <br />efforts of the United Stotes and Mexico, On the bosis of runoff <br />records covering the 52-yeor period 1900 through 1951, studies <br />indicated that the reservoir would yield a certain dependable <br />water supply, which confirmed the results of studies made prior <br />to the consummation of the Mexican Water Treaty in 1944. <br />However, except for one yeor, the water supply for the reservoir <br />since 1951 has been so deficient that the reservoir has been es- <br />sentiolly empty for a considerable portion of the time. <br /> <br />No method for making river and reservoir operation studies <br />has been found thot fully replaces the old accepted method, How- <br />