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<br />Nonrecoverable water losses (Consumptive uses) - water lost to the <br />atmosphere through evaporation and/or transpiration is ultimately re- <br />covered at some other location through the hydrologic cycle, but is <br />nonrecoverable in any operational sense. Such nonrecoverable losses <br />in irrigated agriculture constitute the major source of water loss <br />(60 to 80 percent), and therefore represent the greatest potential for <br />water conservation and improved water use efficiency. <br /> <br />Recharge - the addition of water to an aquifer, normally from surface <br />sources. Natural infiltration and percolation of rainfall or of sur- <br />face waters flowing (diffused or in streams) or stored (lakes) to a sub- <br />surface storage (aquifer) is natural recharge, as contrasted with man <br />induced recharge (artificial) discussed previously. <br /> <br />Recoverable water losses (nonconsumptive destinations) - water which <br />remains on or below the land surface is potentially "recoverable". <br />Although its suitability (quality) for use may be changed, or its <br />accessability (in time, location and/or quantity) may be constrained, <br />the water is not "lost" or necessarily "wasted". Temporary water <br />losses from irrigated agriculture to seepage (5), leakage (L), spills <br />(SP), runoff (RO), or deep percolation (DP) are all properly classified <br />as recoverable water, unless they terminate in some nonaccessable or <br />nonusable place or form (e.g. a highly saline aquifer or sink). <br /> <br />Runoff - excess accumulation of surface waters due to precipitation or <br />irrigation application rates which exceed the infiltration rate of the <br />soil. Depending on soil and slope conditions, surface runoff may vary <br />from zero to ten inches or more annually in the High Plains region. <br /> <br />Scheduling - planned timing and quantity of irrigation water application <br />based on crop growth stage, soil, soil moisture conditions, climatic <br />variations, and evapotranspiration rates to minimize water loss and opti- <br />mize crop yields. <br /> <br />Tailwater - runoff waters from excess irrigation which accumulates at the <br />bottom or "tail" end of fields. Many tailwater recovery systems are in <br /> <br />xii <br /> <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 />I <br />I <br />I <br />I <br />I <br />I <br />I <br />