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<br />compact constraints on the consumption of water by EET's. <br /> <br />~ <br />--.1 <br />~ <br />~ <br /> <br />Irrigated Agriculture. <br /> <br />Irrigated agriculture accounts for about 60 percent <br /> <br />of the Upper Basin's projected depletions in the year 2000. This amounts. to <br /> <br />average annual depletions which range from about 2.6 maf to 2.9 maf, depending <br /> <br />upon which of several different projections one has under consideration. Thus, <br /> <br />if only small percentage reductions in consumption could be attained by <br /> <br />even <br /> <br />improving the efficiency of use, this would translate into relatively large amounts <br /> <br />of water. About 80 percent of the total depletions resulting from the activity <br /> <br />of irrigated agriculture in the Upper Basin are attributable to crop uptake and <br /> <br />transpiration. The other 20 percent is lost under present irrigation practices <br />1 <br />through evaporation or evapotranspiration by noncrop vegetation. Thus, it appears <br /> <br />at first glance that the 2.6 to 2.9 maf of projected depletions for irrigated <br /> <br />agriculture could be reduced by better than 500,000 acre-feet per year. <br /> <br />However, the cost of achieving improvements in irrigation efficiencies will <br /> <br />make the attainment of any such reductions in consumption ess~ntially impossible. <br /> <br />For example, it is estimated that it would cost roughly $700 million to reduce Upper <br /> <br />Basin irrigation depletions by about 130,000 acre-feet per year. While this cost <br /> <br />(about $5,000 per acre-foot) also leads to other benefits, such as improvements in <br /> <br />water quality, it is highly unlikely that improvements in the efficiency of irrigated <br /> <br />agriculture will be a particularly attractive means of making water available for EET's. <br /> <br />1. Water which moves into the ground water system is not, from the prospective of an <br />overall water budget, lost. It simply returns to the hydrologic system, albeit at a <br />different point in time and space. <br /> <br />c~i <br />