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<br />O=ln76 <br /> <br />The average full water supply requirements for the canals between Pueblo <br /> <br /> <br />and the state line exceeds 1,100,900 acre feet per year. Total average <br /> <br /> <br />growing season diversions by the canals, together with the estimated water <br /> <br /> <br />pumped from wells indicate an average annual shortage of almost 340,000 <br /> <br />acre feet in the 1950-1966 period. <br /> <br /> <br />The need for a balanced water supply and the availability of electrical <br /> <br /> <br />power in recent years resulted in the construction and use of numerous <br /> <br />irrigation wells. It has been estimated that, in 1950,31,000 acre feet <br /> <br /> <br />were pumped from wells, and in 1964, the estimated amount is 227,000 acre <br /> <br /> <br />feet. The estimated average pumpage for the 1940-1949 period is 10,600 <br /> <br /> <br />acre feet per year, for the 1950-1959 period 83,000 acre feet per year and <br /> <br />for the 1960-1964 period 168,200 acre feet per year. At present, there <br /> <br /> <br />are more than 1,400 high capacity irrigation wells under the ditches between <br /> <br /> <br />Pueblo and the state line. These wells have an estimated total pumping <br /> <br /> <br />capacity of about 1,770 cubic feet per second. If this rate could be main- <br /> <br /> <br />tained, the pumping capability would be 106,000 acre feet per month. <br /> <br /> <br />It has been estimated by the U.S. Geological Survey that 80 per cent <br /> <br /> <br />of the water pumped is consumptively used and that 20 per cent returns to <br /> <br />the ground water. The depletion of the water resources in the Arkansas <br /> <br /> <br />Valley by pumping, at 80 percent efficiency, would average about 8,500 <br /> <br />acre feet for the 1940-1949 period, 66,000 acre feet for the 1950-1959 <br /> <br /> <br />period and 135,000 acre feet for the 1960-1964 period. In 1964, the depletions <br /> <br /> <br />at 80 per cent efficiency would be about 182,000 acre feet. For a 180 <br /> <br /> <br />day growing season, this maximum depletion in 1964 is equivalent to a Con- <br /> <br /> <br />tinuous flow of 500 cfs. In 1964, the flow at Canon City for the months of <br /> <br /> <br />April through September averaged 860 cubic feet per second. <br /> <br /> <br />Because of the short water supply in the Arkansas Valley, as evidenced <br /> <br /> <br />by the foregoing discussion regarding water resources and requirements, <br /> <br /> <br />and the large impact of wells on the basin water resourCes in recent years, <br /> <br /> <br />computer studies were run on all canals between Pueblo and the state line <br /> <br /> <br />to determine the variations in diver5ions of these canals for conditions, <br /> <br />(1) prior to the construction of John Martin dam and reservoir, (2) after <br /> <br /> <br />the construction of John Martin dam and reservoir, but before the impact <br /> <br /> <br />of heavy well pumping, and (3) after the period of heavy ground water use. <br /> <br />ii <br />