COMPARATIVE STUDY OF EVALUATION OF EVAPOTRANSPIRATION METHODS AND CALCULATION OF CROP WATER REQUIREMENTS AT CHASKAMAN COMMAND AREA IN PUNE REGION, INDIA

Abstract

Accurate estimation of evapotranspiration is necessary step in water resources management. Evapotranspiration varies spatially and temporally. Recently, the Food and Agricultural Organisation has suggested FAO-56 PM method (modified PM method) as a standard method for calculating reference evapotranspiration (ET0), because this method is applicable to all types of season and different climates and gives more accurate result when compared with the physical methods like Lysimeter and Class A Pan. FAO-56 PM method cannot be debated by any other old methods which require less data for calculating ET0. But FAO-56 PM requires very large amount of meteorological data, which is not available at full climate stations. So there is need to find out the next best suitable method after FAO-56 PM method, which will give ETo results nearer to FAO-56 PM method. Here seven different methods are considered for present study, which are radiation based, temperature based and combine parameters based (FAO-56 modified Penman Monteith, FAO-24 Penman Monteith, FAO-56 Hargreaves, Turc, Thornthwaite, Blaney-Criddle, Priestley Taylor are the methods). Chaskaman dam and its left bank canal is selected for this project. The objective of the project work is to calculate daily, monthly and yearly reference ET0 using modified PM equations for ‘left bank canal of Chaskaman dam and its command area’. Further ETc (crop evapotranspiration/crop water requirement) will be calculated for that command area.