Socio-hydrology pathway of grain virtual water flow in China

As the world's largest grain producer, China's activities in virtual water trade for grain are particularly noteworthy. The imbalance of grain production and consumption among regions poses challenges to agricultural development and the sustainable use of water resources. Most of the previous research focused on the driving analysis of factors affecting agricultural water use at the production end. It is necessary to further explore the driving factors of virtual water flow (VWF) caused by grain trade on the consumption side, and consider the impact of production and consumption on the entire process of agricultural water use. This study combines the Logarithmic Mean Divisia Index (LMDI) index decomposition method and multiple regression model to analyze the main natural and social driving factors of VWF. The study also initiates the construction of an analytical framework for the dynamic interaction of coupled social hydrology and Metacoupling systems. The results indicate that economic growth is the primary driver behind the increase in VWF. The water intensity effect and industrial structure effect act as constraints on VWF. Notably, water intensity has the most significant negative effect, with contributions of - 118.9 Gm3 and - 192.4 Gm3 to the virtual water output and input areas, respectively. Conversely, the economic, demographic, and dependence effect play a promoting role. Among these, the positive economic effect far exceeds population and dependence effects, contributing 189.7 Gm3 and 231.3 Gm3 to the virtual water output and input areas, respectively. The analytical framework of coupled social hydrology and the dynamic interaction of Metacoupling systems reveals that VWF couples water resources with multiple systems through the production-consumption-pollution chain. Simultaneously, it achieves long-distance interactions across spaces through cross-space VWF, exhibiting socio-hydrological interactions. The input area displays a forward cycle, while the output area exhibits the opposite. These findings can serve as a theoretical reference for controlling grain VWF.