Irrigation Requirement of Wheat Under Future Climate Change in Northwest Bangladesh

Wheat is an important dry season irrigated crop in the water-scarce Northwest Bangladesh. Knowledge on irrigation requirement of wheat under climate change is crucial for the planning of irrigated agriculture in the region. This study estimated irrigation requirement of wheat for Bogura, Rajshahi, Pabna, and Dinajpur districts for 2050s and 2080s under moderate (RCP4.5) and rapid (RCP8.5) climate change scenarios; RCP indicates representative concentration pathways. The climate scenarios were prepared from the outputs of five global circulation models (GCMs) with a combination of downscaling and bias correction. Reference crop evapotranspiration (ETo), effective rainfall (ER), potential crop-water requirement ( n-ary sumation ETC), and potential irrigation requirement ( n-ary sumation ETC-ER) were estimated by CropWat model. The ER, n-ary sumation ETC, and n-ary sumation ETC-ER were also determined for a base period of 1980-2013 for Bogura district to be used for comparison. The results reveal that ETo would increase during the wheat-growing period, with a greater increase during the development and mid-season stages and also under the rapid climate change compared to the moderate climate change scenario. Both the crop-water and irrigation requirement of wheat would increase due to increased ETo despite an increase in ER to some extent. The average irrigation requirement (over the climate models) would be 5.7% and 13.9% higher during 2050s and 2080s, respectively, compared to the base period under moderate climate change. The highest increase (17.5%) in irrigation requirement would be during 2080s under rapid climate change. The results of this study would be useful for local adaptation of irrigated agriculture to climate change.