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. . . U!)1l88 Shortened Growing Seasons Shortages are handled in a different manner for the CU&L reports than in the CRSS. Shortages are still limited to alfalfa and pasture, but there is no documentation as to how the shortage acreage was developed. As part of the Type I survey, an average irrigation water cutoff date was determined from past irrigation practice. A Representative stream gage within each subarea was chosen. The average historical streamflow that had occurred on the cutoff date was determined. For each year, the recessional portion of the annual hydrograph and the "cutoff flow" were used to determine the date at which the "shorted" water supply should be cutoff. This date served as the end of the growing season for these lands. Incidental Consumotive Use Unlike the CRSS study, incidental consumptive use was considered a function of the net irrigation requirement rather than a function of acreage. The net irrigation requirement is the crop consumptive use less effective rainfall. Incidental consumptive use values, as a percentage of the net irrigation requirement, may have been initially developed for the various river basin studies and the Colorado State Water Plan. For the 1971-75 and 1976-80 report periods, incidental consumptive use was considered to be 28.8 % of the net irrigation requirement, for all sub-basins. For the 1981-85 and 1986-90 report periods, the percentages were modified as presented in Table 8. Table 8. - 1981-85 and 1986-90 CU&L Incidental Use Percentages Hydrologic County Incidental Unit Use 14020001 Gunnison 24.3 % 14020002 Delta 28.8 % 14020002 Gunnison 18.9 % 14020002 Hinsdale 28.8 % 14020002 Montrose 9.9 % 14020003 Gunnison 28.8 % 14020003 Saguache 28.8 % 14020004 De lta 28.8 % 14020004 Gunnison 28.8 % 14020005 De lta 28.8 % 14020005 Mesa 18.9 % 14020005 Montrose 9.9 % 14020006 Delta 28.8 % 14020006 Montrose 28.8 % 14020006 Ouray 6.8 %