Temporal Variability of Potential Evapotranspiration in Response to Climate Change in Ambala District, Haryana, India

Abstract

Potential evapotranspiration (PET) plays a critical role in irrigation planning and is needed for the determination of water demands of crops. The PET trends may have a direct influence on the production of crops, and thus identifying trends in Reference Evapotranspiration (RET) under climate change is important for understanding the effect of changing RET on agriculture. The present study was carried out with the following objectives: (1) to compute the Potential Evapotranspiration (mm/day) in Ambala using Thornthwaite formula, (2) to compute the evapotranspiration at Ambala under arid climatic conditions and (2) to investigate trends in PET using the Mann–Kendall (MK) non-parametric test. In the present study, the non-parametric MK method was used for identifying trends in evapotranspiration and other climatic parameters. First, PET values were estimated through the Thornthwaite method for different time scales using meteorological data for 35 years from 1985 to 2019. PET was found to increase significantly at Ambala during annual, kharif, rabi, pre-monsoon, monsoon and post-monsoon time scales. On probing the causal meteorological parameters responsible for the observed PET trends in the Ambala, it was witnessed that wind speed dynamically influenced the observed PET changes at the annual time scale and all the seven seasons over the Ambala. The study showed highly significant trend in PET observed in Kharif season and found an increasing @ 0.02 mm/day, while Rabi season had increasing trend at less significance. In meteorological season pre-monsoon and post-monsoon season had highly significant increasing trend @ 0.03 mm/day and 0.01 mm/day respectively, whereas monsoon season had a less significance increasing trend. Contrary to all seasons, winter had a non-significant decreasing trend. The results of this study support that the evapotranspiration increases over Ambala. The present study will be useful for estimating the principal crop water requirements accurately under changing climates in the arid region of the Ambala.