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I I I I I I I I I I I I I I I I I I I 3.4 Water Supply The water rights and the water diversions allowed by those water rights have been described in the previous section of this report, and it can be seen that a reliable water supply is available to the Canal Company. In this section of the report, the irrigation water requirements of the Fort Lyon shareholders and the adequacy of the water supply available under the Fort Lyon's water rights were assessed. It should be noted that the use of the Canal System is not limited by the amount of water available to the canal, as the irrigators simply use whatever water is made available to them. According to the Colorado Agricultural Stotistics and conversations with individual farmers, the principal crops grown under the Fort Lyon Canal are alfalfa, corn, grain sorghums, and winter wheat. The annual consumptive irrigation requirements for these crops range from about 14 inches for winter wheat to about 30 inches for alfalfa. The consumptive irrigation requirement can be defined as the volume of irrigation water that is needed to satisfy the crop's evapotranspiration needs so that crop production is not limited by lack of water. Previous engineering studies completed for the Fort Lyon indicate that the efficiency of irrigation under the Fort Lyon Canal averages about 47 percent. This value is based on canal losses averaging 30 percent, lateral losses averaging 10 percent, and farm losses averaging 25 percent. An irrigation efficiency of 47 percent indicates that out of each 100 acre-feet diverted into the Fort Lyon Canal, about 47 acre-feet of water becomes available to satisfy the crop irrigation requirements. Figured with this efficiency value, the headgate diversions that are required to give the Fort Lyon shareholders a full water supply average about 380,000 acre-feet. This volume is substantially greater than the volume of Welter actually available for diversion into the Fort Lyon Canal in most years. The Fort Lyon shareholders, therefore, suffer from water shortages in most years and any improvement in the efficiency of water management and distribution will have significant benefits to the Fort Lyon shareholders. To help overcome some of the water shortages, many individual Fort Lyon shareholders have developed irrigotion wells that withdraw ground water from the "allwial" or "valley fill" aquifer. The uses of these wells are administered by the Colorado State Engineer in compliance with the rules and regulations in effect in the Arkansas River Basin. This project should not be expected to affect the use of these wells, as it is expected that the shareholders will continue to use these wells for supplemental irrigation water and other purposes. 12