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Subpart B - Consumptive Use Requirements <br />Part 683 - Water Requirements <br />SUBPART B - CONSUMPTIVE USE REQUIREMENTS <br />C0683.11 <b) <3) <br />C0683.10 Irrigation climatic zones. <br />(a) The state is divided into seven zones with similar <br />climatic conditions. These areas generally have similar peak <br />period consumptive use rates for alfalfa and grass pasture.. <br />Table C0683.52 lists the applicable irrigated crops in each zone <br />and gives the recommended design peak consumptive use'rate in <br />inches per day for various net depths of application. An 80% <br />chance of effective rainfall was used as part of the input. <br />C0683.11 Monthly consumptive use rates. <br />(a) Water use by crops is influenced by several climatic <br />factors, the mcst significant of which are temperature.and <br />sunlight. Since these values vary from day to day, water use <br />rates will vary also. Consumptive use rates may be computed for <br />any time period, however, monthly values are usually determined <br />because of the availability of climatic data summarized on a <br />monthly basis. Site specific daily data should be used when it <br />is available. <br />(1) Table C0683.50 shows the estimated total consumptive <br />use of water by season and month for various crops, the amount of <br />effective rain-fall, net irrigation requirement for each crop, <br />and growing seasons by crops for 27 weather stations disbursed <br />throughout the seven climatic zones of the State. <br />(b) To determine the amount of irrigation water that should <br />be applied each month, it is necessary to consider the following: <br />(1) The amount of water necessary to fill the root zone to <br />f-i wl d capacity. <br />(2) The amount to be added to each month's needs because of <br />losses attributed to application efficiency. This will vary with <br />soils, the irrigation system, field efficiencies, and the <br />management provided by the operator. <br />(3) The amount to be applied near the end of the use season <br />to restore the soil moisture level to field capacity. Some <br />farmers prefer to add the leaching requirement at this time also. <br />00683-5 <br />(C0210-VI-COIG, December 1988)