Abstract

Evapotranspiration is a vital parameter for irrigation planning and management, and for hydrological and climatological studies. This can be estimated by using Blaney-Criddle (BC), Thornthwaite (TW), Hargreaves (HG) and Penman-Monteith (PM) methods. Out of these methods, BC and TW are known as temperature based whereas HG is radiation based and PM is based on Food and Agriculture Organization (FAO) report on crop water requirements. This paper illustrates a study on comparison on estimates of reference evapotranspiration (ETo) obtained from temperature, radiation and FAO based methods for Surat region. The meteorological data such as air temperature, relative humidity and sunshine hours observed at Surat region for the period 2001 to 2016 is used. In addition, the wind speed and solar radiation data is downloaded from the International Water Management Institute website and used in estimation of ETo using PM. The performance of the methods used in estimation of ETo is evaluated through regression analysis by developing a linear regression between the observed and estimated values of ETo using BC, TW and HG, and FAO based PM. The results of linear regression analysis indicated that there is a good line of agreement between the observed and estimated ETo using PM with CC of 0.968 when compared with those values of BC, TW and HG. The study show that the PM is better suited amongst four methods applied in estimating the ETo for Surat region, Gujarat.