Climate change impacts on reference crop evapotranspiration in North‐West hydrological region of Bangladesh

ABSTRACT Climate change is a critical global environmental challenge that has rigorous impacts on crop‐water demand and a number of other systems, such as hydrological systems and ecosystems. Reference crop evapotranspiration ( ET o ) being a hydrological parameter reflects the integrated effects of various climatic parameters. Consequently, any variations in the climatic parameters induce variability in ET o . This study identified the accountable climatic parameters for the variability of ET o in Dinajpur and Bogra districts of the North‐West hydrological region of Bangladesh. ET o was determined by FAO Penman–Monteith method from the daily weather parameters of the two districts for a period of 21 years (1990–2010). Trends of ET o and its governing climatic parameters over the years were detected and quantified. Correlations between ET o and the governing parameters were determined. The results revealed decreasing trends of ET o in most of the months of the year during the study period in both districts. The climatic parameters causing the observed trends in ET o differed over the months of the year. The combine effects of decreasing net radiation and wind speed, and increasing mean daily air temperature and saturation vapour pressure deficit contributed reducing ET o in the study area. These results, by enhancing our understanding of the effects of climate variability and climate change on ET o , will help sustainable planning of water resources utilization in agriculture of the region.