Comparison of Pan Evaporation-Based Reference Evapotranspiration Model with Penman Monteith FAO-56 Model

The pan evaporation-based model: Christiansen and the combination-based model: Penman Monteith FAO-56 were used to estimate reference evapotranspiration at different locations. Of Assam, India. The locations include meteorological stations at Dibrugarh, Dhubri, Goalpara, Golaghat, Gauhati, Gohpur, Lumding, Margherita, Nagrakata, North Lakhimpur, Sibsagar Silchar, Silicorie and Jorhat. The Penman Monteith FAO-56 model was selected as the standa M of comparison for evaluating the pan evaporation-based model. The criteria of the comparison for the study are the, standard error, coefficient of correlation and root mean square error. The monthly meteorological data of all the above-mentioned stations were collected and were used to estimate the ETO and to carry out the regression analyses. The lowest and highest values of evapotranspiration obtained from Christiansen model were 2.61 mm1day and 8.67 mm1day in the months of December and May at Margherita and Dhubri, respectively. Christiansen model overestimated ETO at all the locations. The RMSE, standard error and the correlation coefficient varied between 2.62 to 4.07; 0.76 to 0.10; and 0.99 to 0.71, respectively.