1 Department of Agricultural Engineering, North Eastern Regional Institute of Science & Technology, Nirjuli, (Itanagar)-791 109, Arunachal Pradesh (India).
2 WTC, I.A.R.I., New Delhi-110012 (India). E-mal: gsagrawal_76@rediffmail.com
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 standard 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 ET0 and to carry out the regression analyses. The lowest and highest values of evapotranspiration obtained from Christiansen model were 2.61 mm/day and 8.67 mm/day in the months of December and May at Margherita and Dhubri, respectively. Christiansen model overestimated ET0 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.
