Dam Regulation Moderates Climate-Induced Rice Yield Loss in the Mekong-Tonle Sap Lake System

Rice, a principal global staple crop, is increasingly threatened by intensified flooding under climate change, placing rice-dependent economies at risk. Yet the potential for human activities to mitigate inundation impacts on rice remains essential and largely overlooked. Here we develop an interdisciplinary agro-hydrological framework that links climate forcing, hydrological regulation, and farmer decision-making from a systems perspective. We apply the framework to the rapidly changing Lancang-Mekong River Basin, focusing on Tonle Sap Lake – a biodiversity hotspot and major floodplain rice-production region-where shifting flood dynamics interact with rainfall-driven planting practices. We project that farmers' rainfall-driven planting decisions will progeressively delay planting, particularly as climate change intensifies, while the hydrological regime will produce more consistently high but less damaging water levels. Relative to a baseline period (1980-2014) with mean annual rice losses of US$78 million, losses are projected to inthe near future (2021-2060), and then increase in the far future (2061-2100). A Joint adaptation strategy combining reservoir operation (dam regulation) with farmer-led shifts towards earlier planting substantially reduces inundation damages and improves climate resilience. We further find that the dominant phenological window of inundation-induced loss shifts from the reproductive and maturity stages (baseline) to the vegetative and reproductive stages in both the near and far future. Reservoir operation primarily constrains losses during the reproductive and maturity stages, thereby limiting late-season damage. This framework enables investigation of coupled water-agriculture dynamics and their growing interdependencies under climate change, supporting robust assessment of climate-resilient adaptation pathways.