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<br />. <br /> <br />. <br /> <br />5 <br /> <br />;~5ather modification increases precipitation which, in turn, <br /> <br />A <br />o <br />~ <br />f\:) <br /> <br />incre&.~es runoff and stream flow. However, the increased runoff will <br /> <br /> <br />bring additional salts into the river system. The impact on salinity <br /> <br /> <br />of inc~eased runoff due to weather modification activities will be <br /> <br />the sa::e as that of increased natural runoff and can be evaluated by <br /> <br />analyses based on historical data. <br /> <br />NEED FOR AUGMENTATION OF THE COLORADO RIVER <br /> <br />Present water requirements of the Upper and Lower Basins, de- <br /> <br />liveries to Mexico, and river losses are about 12 million acre-feet <br /> <br />per year (maf/yr). By 1990, when deliveries to the Central Arizona <br /> <br />Projec~ (scheduled to commence in 1985) will be approaching the <br /> <br />naxim~ and with the completion of several projects now under con- <br />struction in the Upper Colorado River Basin, annual water require- <br />ments are projected to approach 14 maf/yr. Since that is about the <br />level of the dependable yield of the Colorado River system at Lee <br />Ferry, a long-term deficit condition will commence about that time. <br />Growth in water demands is expected to continue after 1990, and a~nual <br />deficits will have to be met by drawdown of water stored in the basin's <br />reservoirs unless the river's flow is augmented starting in the 1990's. <br />While the need for augmenting the Colorado River supply, in terms of <br />timing, cannot be projected precisely because of unknowns such as <br />variations in future water supplies and requirem0nts, it can be <br /> <br />foreseen that, at some time after the turn of the century, accumulated <br />we,ter in reservoir storage will be drawn down to some minimum value <br /> <br />and Basin water uses will have to be reduced. <br />