Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Biological and Irrigation Engineering


A. Alvin Bishop


Water has become one of major national concerns, and it is the limiting factor in the expansion of an irrigated agriculture. Irrigation development is rapidly growing all over the world. New lands are being brought under irrigation and older irrigation lands are being improved. In the planning and operation of an irrigation project, the estimation of water requirements and evapotranspiration, or consumptive use, requires careful consideration. A knowledge of evapotranspiration is playing an increasingly important part in irrigation science. It is the best index of water requirements which represent the amount of water that should be applied by irrigation for normal growth under field condition. Research concerning consumptive use of water by crops grown on irrigated farms has been carried on by various agencies of government in many countries for over fifty years. There is a wide range in consumptive use values under different conditions of climate, soil, cropping pattern, farm management, etc. Irrigation engineers need a better knowledge of consumptive use, or evapotranspiration, and this is true in Thailand.