Mitigating China's food-related water scarcity and spatial inequality via integrated basin-city management.

Food production is constrained by water availability at the basin scale, whereas the governance of food trade primarily operates at the city scale. This spatial mismatch hinders the sustainable development of both food and water systems. To bridge this gap, we develop an integrated framework that combines hydrological (basin) and administrative (city) scales and apply it to China to quantify how virtual water flows embedded in food trade affect inequality in water allocation across and within basins. Our results show that 38% of scarce water is traded across basins, exacerbating interbasin inequality by 6%. In contrast, approximately 30% of scarce water is embodied in intrabasin trade, which alleviates intrabasin inequality. Single-scale interventions, whether through production or consumption adjustments, involve trade-offs among interbasin equality, intrabasin equality, and total water savings. By contrast, an integrated basin-city management strategy at a 50% intervention intensity reduces interbasin inequality by 7% and achieves water savings equivalent to more than four-fifths (80%) of total water use in the Yangtze River basin. It also outperforms existing province-city vertical management models across scales. These findings provide valuable insights for developing global virtual water management strategies that integrate both hydrological and administrative perspectives.