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<br />pumping, on the state line flows. It is possible that pumping <br />of the supplemental irrigation wells was greatly reduced <br />during the recent period of above average water supply. <br />Kansas' Interpretation of the Mass Analyses <br />In addition to the discussion of the mass diagram <br />analyses in Kansas' first report of September 4, 1985, <br />Kansas' conclusions are necessarily premised on its under- <br />stanping of: 1) ground water development in Colorado; 2) <br />return flows from transmountain diversions; 3) criteria <br />relevant to the selection of an index inflow; 4) the initial <br />use of the John Martin conservation pool; 5) the effect of <br />the 1980 Storage Resolution; 6) the comparative significance <br />of the drought of the 1970s with previous droughts; and 7) <br />the effects of major flood events. <br />1. Groundwater Development and Use in Colorado <br />Wells tapping the alluvial ground water of the Arkansas <br />River have evolved as a significant source of supplemental <br />irrigation supply in Colorado. Beginning in the late 1940s, <br />the number of alluvial wells increased dramatically until <br />1973,when well development was finally curtailed by the <br />Colorado State Engineer. Most of this development ~ccurred <br />between 1950 and 1965. A U.S.G.S. report prepared in 1970 <br />states that "during this 15-year period about 1,000 wells <br />were drilled. . . [and that] (w)ithdrawal of groundwater by <br />wells increased from 31,000 to 185,000 acre feet annually in <br />,this period." Complete ,and accurate records of groundwater <br />pumping'are not maintained. Quantification of groundwater <br />usage is therefore approximate. <br />-21- <br />