Evaluating the impact of climate change on irrigated rice in Indo-Gangetic Plains of India using CMIP6 data

In the present work, we aim to quantify the impact of climate change on the phenology, water requirement, and grain yield of irrigated rice in the Uttar Pradesh state of India. Uttar Pradesh, located in the heart of the Indo-Gangetic Plains, is the biggest agrarian state in India, with around 17 million hectares cultivable land, and 205 million population. We used BCC-CSM2-MR (Beijing Climate Center Climate System Model) and EC-Earth3-Veg (Earth-Consortium-Earth3-Veg) for SSP245 (Shared socio-economic pathway 245) and SSP370 scenarios from CMIP6 (Coupled Model Intercomparison Project Phase 6). We bias-corrected and statistically downscaled the climate model data. We used the climate data to force the DSSAT (Decision Support System for Agrotechnology Transfer) crop model. We used the calibrated crop data (cultivar information, management practices), soil data, and observed weather data (1980-2010) in the DSSAT model, provided by IMD (India Meteorological Department). We designed 12 sets of experiments (consisting of 4 rice cultivars and three sowing dates [early, mid-season and late]) for 242 locations in Uttar Pradesh for observed weather, and climate model (for both SSP245 and SSP370 for period 2015-2050) data. We found that the average amount of seasonal rainfall over Uttar Pradesh decreases up to 4 to 8% and 35 to 40 % for SSP245 and SSP370, respectively. The irrigation amount increases for both SSPs; however, the rise in SSP370 is almost triple the value of SSP245. Notably, the difference between irrigation amount from present to projected climate decreases for late sowing crops. Seasonal crop evapotranspiration increases in the range of 4 to 12% and 8 to 16% for SSP245 and SSP370, respectively. The anthesis and maturity days are advanced by approximately 2 to 7 days. The rice yields are expected to increase by 12 to 17% and 24 to 30% for SSP245 and SSP370, respectively.