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<br />means of estimating or predicting ET rates consistently over time without <br />direct measurement of local climatic and soil moisture conditions. <br />Fortunately, fairly dependable, inexpensive and simple devices are now <br />available to measure soil moisture and therefore to estimate ET rates and <br />facilitate improved irrigation scheduling for proper timing and quantity <br />of irrigation. These devices will be discussed in detail in a later section. <br /> <br />A significant variety of management, cultural and land treatment prac- <br />tices are available which can be used to influence ET rates. These will be <br />accessed individually, with ET relationships noted. Most water conservation <br />and water use efficiency practices have some degree of impact on ET rates. <br /> <br />SURFACE RUNOFF AND DEEP PERCOLATION REDUCTION <br /> <br />Most of the other so-called water losses (or wastes) from irrigated <br />agriculture can be lumped together in the category of recoverable losses, <br />as previously defined. Although these losses may take many forms and result <br />from a great variety of causes or situations, all recoverable waters ulti- <br />mately end up as surface runoff (water which accumulates on the soil surface <br />at rates faster than the soil infiltration rate) or as waters which pass <br />through a saturated soil profile to below the effective root zone of growing <br />plants (deep percolation). Such recoverable losses typically constitute only <br />10 to 30 percent of water use in High Plains irrigation and can be substan- <br />tially reduced through available water management practices. <br /> <br />Temporary (recoverable) water losses occur during all phases of <br />irrigation; storage, conveyance, application, recovery and reuse, pumping, <br />etc. Spills, leaks, seepage, runoff and deep percolation are all sources <br />of these losses. Inevitably, some evaporation and transpiration (by non- <br />productive plants) occurs during each of these activities as well, but these <br />are part of the total ET losses in water use efficiency calculations. <br /> <br />Conservation improvements or water use efficiency practices related <br />to "recoverable" water losses can be classified into three broad categories: <br />1) recovery and reuse of waters on the farm, as efficiently and inexpensively <br />as possible; 2) reduction or minimization of losses to reduce initial water <br /> <br />6 <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 />