Estimation of evapotranspiration by wheat in Pantnagar Tarai

Lysimetrically measured seasonal evapotranspiration (ET) of rabi wheat under Pantnagar tarai region of Uttaranchal ranged between 520.7 and 524.9 mm. The potential ET (PET) estimated by a newly developed weather data based equation was found to be correlated with measured ET at 0.1% level of significance (r = 0.956 to 0.969) consistently over three consecutive years with the least under/overestimation (−0.9 to +1.9%). The pan PET method ranked second, followed by Turc and Stephen-Stewart methods in this respect, while pan evaporation showed the poorest relationship with the measured ET. The crop coefficient estimated in the proposed method increased steadily to a maximum during fifteenth week of crop and then decreased rapidly following senescence at end of season.