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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />r <br />I <br /> <br />001535 <br /> <br />Both petroleum and coal are produced in ASA 11, though not in large <br />quantities. Much of the region, with the exception of the southeastern <br />corner, has deposits of coal and possibly petroleum. Expansion will depend <br />on whether these resources will be competitive with supplies from outside <br />the area. Nonmetallic mineral production requiring large amounts of process <br />water is tied closely with the three major metropolitan centers in the area. <br /> <br />Crop Irrigation <br /> <br />Monthly and annual irrigation water use coefficients were developed by <br />the U.S. Soil Conservation Service to aid in determining the water resource <br />base. Crop consumptive irrigation requirements, irrigation system conveyance <br />efficiency and on-farm efficiency estimates were developed to reflect current <br />and future water-use efficiencies. These estimates were applied to the MCC <br />acreages to provide monthly and annual irrigation requirements for the full <br />water supply situation. Crop consumptive irrigation requirements were computed <br />using the modified Blaney-Criddle method. Conveyance and on-farm application <br />efficiencies were compiled from existing file records and recent reports. <br />Data were developed for the 1975, 1985 and 2000 time frames, based on recent <br />trends of improving irrigation systems and management. The water withdrawals or <br />gross diversion requirements equal crop consumptive irrigation requirement <br />divided by system efficiency. <br /> <br />The MCC consumptive use estimates represent the dry year (2 out of every 10 <br />years) requirement value, or that amount of water required to support excellent <br />crop production without crop stress. A value for an average year requirement - <br />that water required to support crop production without crop stress when average <br />precipitation occurs - was also computed, but is not included in either the CC or <br />the MCC data furnished. <br /> <br />Neither of the computed water requirements values for irrigation reveal the <br />actual amounts of water diverted or consumed for irrigation. The lack of adequate <br />records does complicate any determination of actual water use for irrigation. <br />Since crop irrigation constitutes about 85 to 90 percent of the total functional <br />water use in the basin, it is more important to the region to obtain the <br />best possible estimate of actual current water use rather than the theoretical <br />water requirement value. Comparing the theoretical requirement to the actual <br />water use will reveal the magnitude of the water shortage problem. However, <br />it does not reveal the specific areas within each ASA with a water short problem <br />or the magnitude or nature of the problem for specific areas. Including <br />theoretical crop irrigation water requirements for the dry year condition in <br />the MCC tabulations, which have the headings "Annual Water Requirements," <br />"Withdrawal Use" and "Consumptive Use" is misleading.' Unless one is thoroughly <br />familiar with the derivation of the data, the impression is incorrectly made <br />that considerably more water is used for crop irrigation than is actually the <br />case. Subtracting these values from the available supply results in understating <br />the remaining supply available; or worse, adding these values to the supplies <br />indicated as being available based on stream-gaging records, overstates the <br />available water supply. This has serious implications concerning hydropower <br />generation capability, maintaining adequate flows for Missouri River navigation <br />(Sioux City, Iowa, to the mouth), availability of water to increase crop produc- <br />tion by additional irrigation, availability of water for energy and coal field <br />developments, and actual instream flows available for fish, wildlife, water <br />quality, maintenance of ecosystems, and environmental needs. Any evaluation <br />of irrigation water use in the Missouri River Basin should consider the reservoir <br />storages provided, use of ground water and actual experienced shortages. It <br />is a complex problem with many variables. While water requirements and actual <br /> <br />III-7 <br />