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<br />0=' 1955 <br /> <br />Arkansas Valley is consumed and 20% returns to the ground water aquifer. <br /> <br /> <br />Using these values, depletion of the water resources in the Arkansas Valley <br /> <br /> <br />by pumping would have averaged about 8,500 acre-feet from 1940-1949. 66,000 <br /> <br />acre-feet from 1950-1959. and 135,000 acre-feet for the 1960-1964 period. <br /> <br /> <br />The depletions for 1964 would have approximated 182,000 acre-feet, or the <br /> <br /> <br />equivalent of a continuous flow of 500 cubic feet of water per second over <br /> <br /> <br />a 180 day growing season. By comparison, the flow at Canon City for 1964 <br /> <br /> <br />from April through September averaged 860 cfs. <br /> <br /> <br />As a result of the short water supply in the Arkansas Valley, computer <br /> <br /> <br />and mass diagram studies were run on all canals between Pueblo and the <br /> <br />state 1 ine. The studies were directed toward a determination of possible <br /> <br /> <br />variations in canal diversions for conditions (I) prior to the construction <br /> <br /> <br />of John Martin Reservoir. (2) after its construction, but before heavy <br /> <br /> <br />ground water use, and (3) during the period of heavy ground water use. <br /> <br />Computer studies were made of the flow at the Canon City gage and <br /> <br /> <br />the outflow at the State line to determine inflow-outflow trends for the <br /> <br /> <br />aforementioned three periods. The average annual flow at the Canon City <br /> <br />gage from 1924 through 1966 was 518,000 acre-feet. Flows were corrected <br /> <br /> <br />for diversions around the gage and other influences. If the flows in the <br /> <br /> <br />exceedingly high runoff years of 1942 and 1965 are excluded from the <br /> <br /> <br />study, the Canon City flow for pre- and post-John Martin conditions averaged <br /> <br />478.000 and 524,000 acre-feet respectively. The lower average flow reflects <br /> <br /> <br />the drouth of the 1930's for pre-John Martin conditions. <br /> <br /> <br />The outflow at the state line prior to the construction of John <br /> <br /> <br />Martin Reservoir (1924-1942) averaged 194,000 acre-feet, whereas it has <br /> <br /> <br />decreased to 175,000 acre-feet during recent years. The high runoff years <br /> <br /> <br />of 1942 and 1965 were excluded from these averages. <br /> <br /> <br />A mass diagram analysis of the state line flow vs. the Canon City flow <br /> <br /> <br />indicates an average loss from 1951 through 1966 at the state I ine of <br /> <br /> <br />approx;mately 105,000 acre-feet. The 1951 through 1966 period of study <br /> <br /> <br />includes periods of concentrated ground water withdrawal with higher <br /> <br /> <br />average annual depletions than for the 1942 through 1966 period. <br /> <br /> <br />Mass diagram studies of canal diversions from 1951 through 1966 <br /> <br /> <br />reveal an average annual decrease of approximately 113,000 acre-feet, <br /> <br />10 <br />