Water is the basic need for life existence. In the hydrologic cycle the evapotranspiration plays a vital and complex role. Estimation of Evapotranspiration (ETo) in a accurate manner is essential for all the practices of water management in a efficient way especially for agricultural based developing country India. This paper investigates the estimation of evapotranspiration models in agricultural industry mainly for paddy production. India is the second largest producer of rice in the world, it requires high temperature above 250c with annual rainfall above 100 cm, mainly grown in north and north-eastern India, coastal and deltaic reason.  The performance of the model was evaluated by using the statistical parameters such as Correlation coefficient (R2) and  root mean square error (RMSE), the water losses due to evapotranspiration in surface water can be determined.  

Keywords: Evapotranspiration, penman-monteith, FAO56, Pan Evaporation, Kancheepuram district