Comparison of Different Approaches of Computation of Evapotranspiration

Evapotranspiration (ETo) plays a wide role in planning of irrigation-system. Evaluation of ETo by FAO-56-Penman-Monteith (FPM-56) model require detailed meteorological data, but in developing countries which like India, such data are not easily available. In this research, different approaches of the ETo like temperature, radiation, pan evaporation and mass transfer equations were computed against the FPM-56 model and best alternative was found out. If the detailed weather data for FPM-56 is not available then in such situation alternative was selected from each of the above approaches. Comparison of all approach methods of ETo with FPM-56 shows ten best methods, which include three radiation, three temperature, three were the pan evaporation and one from the mass transfer methods. The best suited method from each approach was compared with FPM-56 and arranged with their RMSE value. It is found that McGuinnessBordne was the best alternative among the available methods. Also, the average of all the methods of each approached was compared with FPM-56 and it is observed that temperature based approach can be considered as alternative.