Coupled climate–land use change impacts on the water–food nexus using the soil and water assessment tool plus (SWAT+): Application to the Condamine–Balonne River Basin, Australia

Climate and land-use change (CLUC) jointly reshape water availability and agricultural productivity in semi-arid basins, with consequences for water–food security. This study quantified climate-only (CC) and combined CLUC effects in the Condamine–Balonne River Basin (CBRB), Australia, using the Soil and Water Assessment Tool Plus (SWAT+). Bias-adjusted CanESM2 projections (CMIP5 RCP4.5; Quantile Delta Change) were integrated with Land-Use Trade-Offs (LUTO) projections and Cellular Automata–Markov (CAM) modelling for a 2000–2025 baseline and eight future decades (2030s–2100 s). By the 2100 s, maximum temperature increased by 3.2–3.5 °C, annual precipitation declined by 11.77%, and land use progressively shifted from irrigated cropping towards pasture-dominated landscapes. Under CC, potential evapotranspiration (PET) and actual evapotranspiration (green-water consumption) increased by 16.94% and 10.66%, respectively, while surface runoff, groundwater recharge and lateral flow declined by 26.74%, 10.73% and 24.26%. Consequently, blue water (surface runoff plus baseflow) decreased from 195.41 to 143.96 mm yr⁻¹ (−26.33%). Under CLUC, potential evapotranspiration (PET) and green-water consumption increased by 19.94% and 11.55%, whereas surface runoff, groundwater recharge, lateral flow and blue water declined by 27.78%, 12.54%, 28.15% and 27.84%, respectively. Major crop yields declined by approximately 12% in the 2030 s and 33% by the 2100 s. These findings reveal a progressive shift from blue-water availability towards greater atmospheric demand and green-water consumption, intensifying irrigation pressure, recharge constraints and agricultural vulnerability. The results support improved irrigation efficiency, soil-water conservation, climate-resilient cropping and coordinated surface-water–groundwater allocation for sustainable basin management.