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<br />9 <br /> <br /> <br />wastes, and pesticides. Crop cooling to ensure continued <br /> <br />W <br />N <br />,.... <br />o <br /> <br />growth, and frost protection are additional benefits (Figure <br />1). Partial control of date of maturity and subsequent <br />early harvest of crops such as fruits, vegetables and <br />flowers may also be achieved through irrigation (2). <br /> <br />!H!9:s!!2!! B~!J!:!! ng~ <br /> <br />of the total water applied during irrigation, as much <br />as 65 percent may be used consumptively. This use includes <br /> <br />loss by direct evaporation from the soil plUS transpiration <br /> <br />from plants. Consumptively-used water is that discharged <br />into the atmosphere as vapor and is no longer available for <br /> <br />reuse within or by the existing system. The balance of the <br /> <br />applied water, or about 35 percent, is termed irrigation <br /> <br />return flow and finds its way back into the surface or <br />subsurface hydrosystem. Irrigation return flow then, is the <br />water diverted for irrigation which returns to the surface <br /> <br />stream or to the subsurface ground water environment (3). <br /> <br />The practice of irrigation necessarily degrades the <br />quality of applied water to some degree inasmuch as the <br /> <br />water is used consumptively. Evaporation and transpiration <br />alone may concentrate dissolved minerals in the applied <br />water as much as 300 percent. In addition to an increase in <br /> <br />salinity, the applied water may acquire sediments, <br /> <br />;L.i -i <br />