A Climate–Hydro–Crop Modeling Framework for Assessing Climate Change Impacts on Hydrometeorology and Rain-Fed Paddy Yield in the Pampanga River Basin, Philippines

Climate change poses a significant threat to water and food security, necessitating an urgent need to quantify the evolving climate-related risks within the water-food nexus. Despite extensive research on climate change impacts on hydrometeorology, the climate–hydro–crop nexus remains underexplored. This study integrated downscaled and bias-corrected MRI-AGCM-3.2S climate outputs, a seamless hydrological model, and a rain-fed paddy model to simulate the climate change impacts on hydrological extremes, water availability, and rain-fed rice yield in the Pampanga River basin under the RCP8.5 scenario. The results showed a marginal increase in annual rainfall, accompanied by greater temporal and spatial variability. Extreme rainfall and associated flood events were projected to be more frequent and intensified. Despite the increase in basin-averaged annual rainfall, the annual discharge at San Isidro was projected to decrease due to weakening post-monsoon rainfall. The projected basin-averaged rain-fed rice yield showed a modest decrease at the basin scale, with larger losses in the eastern region due to water stress and in low-lying areas due to flooding compared to the past climate. These findings highlight the growing hydrological and agricultural risks posed by climate change in the basin and thus require regional climate-adaptive and climate-resilient strategies to safeguard water-food security. Future research will include intensive data collection, a comprehensive sensitivity assessment, and the integration of irrigation practices and the water storage function.