Assessment of climate change impacts on crop water requirement in the Sundarban region of coastal West Bengal

Abstract

Climate change is considered as the major threat to the sustainability of the fragile ecosystem of Sundarbans with serious impact on the agricultural production thereby threatening food and livelihood security of the resource poor farmers. With rising temperatures and changes in rainfall pattern, climate change would affect the water balance, as well as, water requirement of agricultural crops. Effective rainfall, crop ET and irrigation water requirement of rice, maize and tomato for the post rainy season (rabi) were estimated with CROPWAT model using the downscaled MarcSim weather data (2016-75) for RCP 6.0 (IPCC-AR5) scenario obtained from an ensemble of all 17 GCMs and using the actual weather data for the base period (1966-2015). Though the average decadal rainfall, effective rainfall and reference ET were lower for the MarcSim generated data in comparison to the observed data for the base period, there was an increasing trend of these parameters during 2016 – 2075. The increase in decadal crop ET varied from -1.32 to 1.27 %, -0.15 to 12.50% and -7.45 to -5.08% over the base period for rice, maize and tomato, respectively. On the other hand, the effective rainfall during the crop growth period reduced by 21 to 29 % over the base period. The decadal irrigation requirement for the different crops showed an increasing trend and was highest during the 2066-75 decade for maize (12.5%) as compared to rice (5.8%) and tomato (2.6%). Advancing the sowing time for the crops led to a decrease in the irrigation requirement, while delayed sowing attributed to higher water requirement of the crops.