Selection of the Best Method of ETo Estimation Other Than Penman–Monteith and Their Application for the Humid Subtropical Region

Abstract

Evapotranspiration (ET) is one of the largest components of hydrological cycle, and its accurate quantification is needed in water allocation, irrigation management, and to protect surface and ground water quantity and quality. So there is a need of improved techniques for accurate quantification of ET to enhance efficient use of water resources and sustainability of agro-ecosystem productive. A number of methods have been developed till now for ETo estimation, but most of them are only applicable in areas where they have been developed. Till now, only the Penman method has been accepted worldwide which is acceptable in almost all climatic conditions, but the only major drawback of this method is the large number of data requirement. Therefore, in this study, we have used four reference ETo estimation methods which include two radiation methods (Turc and Priestley–Taylor), one temperature (Hargreaves), and one combined method (Penman method) of ETo estimation. The weekly average meteorological data for the period 1975–2005 were used here to estimate ETo. This study has attempted to select reliable reference ET estimation method other than Penman where less input variables are required. Here, Penman-derived ETo has been selected as the standard for evaluating the performance of other methods of ETo estimation. This study has further attempted to demonstrate some of the significant applications of estimated ETo. The execution of all radiation- and temperature-based methods shows that outcome of Turc-derived ETo is comparable with Penman-derived ETo, and thus this can be used for ETo estimation for this region other than Penman method.