Comparative evaluation of different reference evapotranspiration models

The study was carried out to select best alternative method for the estimation of reference evapotranspi-ration (ET0). Accurate estimation of potential evapotranspiration is a necessary step in water resource management. Recently, the FAO-56 version of Penman-Monteith equation has been established as a standard for calculating ref-erence evapotranspiration (ET0) which requires measurement of a number of meteorological parameters namely, air temperature, relative humidity, solar radiation, and wind speed which may not be available in most of the meteoro-logical stations. Still there are different approaches (requiring less data) which estimate ET0 closely to Penman- Monteith (P-M) method for different climatological conditions. The present study is based on analysis of long term of 13 years (2000 to 2012) climatic data to calculate monthly reference evapotranspiration for Capsicum production (September–March) and also to compare the performance of evapotranspiration equations for Jhalawar district of Rajasthan with the standard FAO-56 Penman-Monteith method on the basis of the least root mean square error (RMSE) analysis. Hargreaves method and Pan evaporation (E-Pan) method overestimated the values of ETo when compared with FAO-56 Penman-Monteith method. On the basis of lowest value of RMSE, Pan evaporation method is found best alternative method to FAO-56 Penman-Monteith method in the study area