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<br />"'~"-'?') <br />u" I., ~ , <br /> <br />are cited as indicating the waste and inefficiency of irrigated agriculture. However, because <br />this water returns to the stream and is available for use by downstream appropriators, the <br />pejorative term "waste" should not be automatically applied to this increment of water. <br />Again at least a portion of this water is being used beneficially to transport water to the <br />crop area. To decide if water is "wasted" or not the observer must determine whetber any <br />other use (decreed or not) is deprived of water due to tbe losses resulting from tbe <br />irrigator's actions and whether or not those losses are reasonable and necessary. Often <br />return flows help meet the late season water supply needs of other users. In tbe Soutb <br />Platte basin return flows get re-diverted downstream some three times before reacbing <br />Julesburg. <br /> <br />The remainder of the water diverted for irrigation is available for consumptive use <br />by the crop. This use involves root uptake of soil water previously delivered to tbe crop's <br />root zone, evapo-transpiration by the plant and incorporation into tbe plant tissues. This <br />consumptive use is the ultimate beneficial use for which the diversion was made. When <br />certain irrigation techniques are employed more water is delivered to the root zone than can <br />be retained by the soil, Deep percolation occurs whenever gravity moves water from soil <br />that is too wet, to a level below wbich a crop's roots can no longer reacb it. This water <br />continues moving downward until it reaches the water table, signifying the presence of an <br />aquifer. Once in an aquifer (eitber seasonal or permanent) deep percolation water normally <br />begins moving toward tbe stream from which it was diverted, unless a geologic barrier <br />prevents that. <br /> <br />In regions where the irrigation water supply contains salts some deep percolation is <br />necessary to maintain a salt balance in tbe soil. Extra water is intentionally applied to the <br />field to leach out salts deposited in the soil by previous irrigations, and carry them below <br />the root zone where they no longer binder plant growth. <br /> <br />The information illustrated by tbe water budget sbows tbat an irrigation diversion <br />results in consumptive uses or depletions and return flows. Depletions can be furtber <br /> <br />5 <br />