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<br />. <br /> <br />. <br /> <br />. <br /> <br />llATER SUPPLY <br /> <br />fiater ~u2rlies available for development by authorized units of the <br />Colorado River Storage project a~d participating projects have been esti- <br />mated on the basis of recorded flows, with consideration given to down- <br />stream uses and past and anticipated upstream depletions. It is not <br />within the scope of this report to summarize the water supply studies <br />made for each participating project. A brief sUJn.'llary of the water supply <br />available to the Upper Colorado River Basin and units of the storage proj- <br />ect is presented in the following paraeraphs, however, in view of the <br />importance of .~ter supply as related to project power production and <br />revenues. <br /> <br />Strearnflows <br /> <br />Three terms are corrmonly used to define flows of the Colorado River. <br />Historical flows are those which have actually occurred. Virgin flows <br />are the estimated flows which would have occurred without man-made derle- <br />tions. Present modified flows are those which would have occurred in <br />the past had the present level of development and depletions been in <br />full effect. <br /> <br />Average annual historical and present modified flows at units of <br />the storage project have been estimated as shown in the following table. <br /> <br />Average annual flows for 1911~-45 period!! <br />(Unit--acre-feet) <br />Historical <br />Unit flow <br />Glen Canyon 13,763,000 <br />Flaming Gorge 1,636,000 <br />Navajo 1,260,000 <br />Curecanti (Morrow Point Dam site) __b_2].Q~000 <br />!/ Period adopted in negotiations for the Upper Colorado <br />Basin Compact as representative of long-time flow conditions. <br /> <br />Present <br />modified flow <br />13,064,000 <br />1,615,000 <br />1,244,000 <br />1,27<::,000 <br />River <br /> <br />At a point 15 miles below Glen Canyon Dam site, the Paria River con- <br />tributes an average of about 25,000 acre-feet annually to the Colorado <br />River, but the flow is erratic from year to year. For all practical pur- <br />poses the flow at Glen Canyon approximates the flow at Lee Ferry, 16 milp~ <br />downstream, the dividing point on the river between the upper and lower <br />basins. The average annual virgin flow at Lee Ferry over th" 19111 ,115 <br />period is estimated at about 15,6110,000 acre-feet. <br /> <br />16 <br />