TREMENDOUS international scien-1 tific effort has been expended on evaporation and transpiration problems during the past decade as evidenced by hundreds of technical publications, and numerous conferences. 'However, use of this scientific achievement by agriculturalists, project planners and operators of irrigation farms has lagged behind technological advancements. The lag in adaptation of new technology by the user can be partly attributed to a lack of time, technical training and experience in meteorology, physics and agronomy. One of the greatest potential applications of evapotranspiration technology is in the management of irrigation farms. Recent studies in the Western States indicate that the timing of irrigations and the amount of water applied have changed very little during the past 25 years. Irrigation scheduling is a decision-making process repeated many times each year, involving when to irrigate and how much water to apply. Both criteria affect the quantity and quality of the crop. Decisions delayed a week, or even a few days, may be costly. Measurements are required to determine when the soil moisture reservoir is full, half-full, or nearly empty. Furthermore, the depletion of soil moisture is complicated because it is determined by meteorological conditions, the growing crop and the unsaturated hydraulic characteristics of the soil. Instruments are available to help determine the soil moisture status, such as tensiometers, soil moisture blocks and the more complicated neutron meter, but these are not used extensively. For these and other reasons, the modern farm manager is generally willing to hire a service that will provide the necessary data and guidelines to assist him in making better and inure profitable decisions. To satisfy such requirements, we developed user-oriented methodology to enable districts, service companies, or mutuals to routinely provide additional information to the irrigation farm man-Paper No. 69-041 was presented et the 1S'inter Meeting of the American Society of Agricultural Engineers at Chicago, 111., Detenibr 1969, on a program arranged by the Structures and Environment Division.