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<br />000732 <br /> <br />Upper Basin State officials believe that the Upper <br />Basin should be allowed to deplete in the range of 6.3 maf <br />to 6.5 maf annually. The principal difference between the <br />estimate of the Upper Basin States of 6.3 and the 5.8 <br />maf estimated by the Bureau is the .75 maf depletion charge <br />to the Upper Basin for planning purposes. <br /> <br />Although the Upper Basin may not reach the estimated <br />5.8 maf amount by the year 2030, a comparison of the Bureau's <br />estimates of average long-term water supply of about 14.8 maf <br />with future projected depletions for the total Colorado River <br />indicate that the river is approaching the point when the <br />natural water supply will be inadequate to meet all the <br />demands placed on it. Future depletions, as estimated by the <br />Bureau, are presented in the following table. <br /> <br /> Annual use <br /> 1975 1990 2000 <br /> (maf) - - - - <br />Upper Basin 3.61 ~/ 5.29 ~/ 5.50 <br />Lower Basin 6.21 7.28 7.37 <br />Mexico 1.66 1.51 1.51 <br />River losses <br />below Hoover Dam .67 .73 .73 <br />Total 12.15 14.81 15.11 <br /> <br />I . <br />, <br />, <br /> <br />~ <br /> <br />a/Upper Basin officials stated that these depletions may be <br />- overstated because of the administration's current position <br />on future development. <br /> <br />Using a mathematical simulation model and assuming <br />an average annual virgin flow of about 14.8 maf, the Bureau <br />has conducted several studies of how the Colorado River <br />and its storage reservoirs are operated. These studies <br />involved analyzing 13 different water supply sequences <br />for the historical period 1906 to present and were modified <br />to reflect projected depletions in future years. Some of the <br />earlier studies showed that sufficient water would be in the <br />river system to meet basin water demands until sometime after <br />1985 when the Central Arizona Project (CAP) is scheduled to <br />make initial deliveries. After this period, the river will <br />probably not yield enough water under normal circumstances <br />to meet all basin demands, the Mexican treaty obligations, <br />and river system losses. More recent Bureau studies indicate <br />that a shortage of water could occur as early as 1992 and <br />probably would occur prior to 2023. However, these studies <br /> <br />11 <br />