Multi-scenario analysis of wheat irrigation requirements under climate change: assessment of CMIP6 models for crop water modeling in Bangladesh

ABSTRACT Multi‑scenario flowchart showing CMIP6 climate models → bias correction → CROPWAT model → wheat irrigation projections for Bangladesh under SSP1‑2.6 to SSP5‑8.5, with temperature as dominant driver. Climate change poses a significant threat to wheat production in Bangladesh, a staple food. This study projects future irrigation requirements for wheat in Mymensingh by integrating an ensemble of five CMIP6 climate models with the FAO CROPWAT model, employing rigorous quantile-mapping bias correction and out-of-sample split-sample validation. Four emission scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5) were analyzed across near (2026–2050), mid (2051–2075), and far (2076–2100) futures. Projections indicate progressive warming, with January maximum temperatures increasing by up to 21.71% under SSP5-8.5 by late century. Consequently, potential crop water requirements rise from 1.38–3.87% near-term to 15.06% under SSP5-8.5 in the far future. While some precipitation increases were noted, their benefits are offset by rising evapotranspiration. Irrigation scheduling will be compressed, with the third irrigation advancing by one week under higher emission scenarios. Sensitivity analysis identified temperature as the dominant driver, increasing irrigation demand by up to 17.19% when isolated; this represents an upper-bound estimate as CROPWAT excludes CO2-mediated stomatal effects. A 20% reduction in soil moisture significantly altered irrigation efficiency. Substantial inter-model variability underscores projection uncertainty, reinforcing the necessity for adaptive, climate-resilient water management strategies to safeguard wheat productivity and national food security in Bangladesh's evolving agricultural landscape.