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• Grain water-carbon footprint was accounting in mainland China. • Grain virtual water-carbon flow among regions was evaluated in mainland China. • Water saving and carbon emission reduction based on grain transfer were evaluated. • Challenges and opportunities in water-saving and carbon emission reduction were discussed. Water resource and carbon emission involved in grain production in mainland China are redistributed among provinces as the grain was transported in recent years. This study first calculated the water consumption and carbon emission during the growth of grain crops based on the water-carbon footprint theory, and then used the social-equity method to calculate the inter-regional grain virtual water and virtual carbon flow. Finally, the regional and national trends in water saving and carbon emission reduction were calculated based on the spatial and temporal differences in grain planting among provinces. In terms of virtual water-carbon, from 2000 to 2017, the amount of the inter-provincial grain virtual water flow increased from 717.4 × 108 m3 to 1472.6 × 108 m3. Heilongjiang and Guangdong are the provinces with the largest amount of grain virtual water outflow (670.9 × 108 m3) and inflow (402.8 × 108 m3) in 2017, respectively. And the total inter-provincial grain virtual carbon flow increased from 2362.7 × 104 t CO 2 e to 12,680.6 × 104 t CO 2 e. Grain transport leads to water saving and carbon emission reduction, the amount of water saving increased from 25.6 × 108 m3 to 77.0 × 108 m3 and the carbon emission reduction increased from 2.4 × 104 t CO 2 e to 847.4 × 104 t CO 2 e from 2000 to 2017. Based on research results and from the perspective of socio-hydrology combined with water saving and carbon emission reduction, the regions could optimize the integration of water saving, carbon emission reduction, and sustainable development based on coordinating the grain planting structure according to their own climatic condition, soil and water resource condition, and socioeconomic condition. [Display omitted] [ABSTRACT FROM AUTHOR]

• The flow pattern of grain virtual water in Chinese Mainland was shown. • Constructing a virtual water flow trade gravity model based on socio-hydrology theory. • Quantifying the driving force of grain virtual water flow using trade gravity model. • Analyzing the response trajectory of virtual water flow under the shock of variable fluctuation. • Research deficiencies and future research directions were given. To ensure regional grain security, the grain is transferred from grain surplus provinces to grain deficient provinces in China, then water embedded in grain (virtual water) flows accordingly, which promotes the spatial redistribution of water resources. To explore the influencing factors of virtual water flow, this study first obtained the inter-provincial virtual water flow pattern, and then constructed a virtual water flow trade gravity model based on socio-hydrology theory and estimated the model with multiple regression methods. And the impulse response function was used to analyze the response trajectory of virtual water flow under the shock of other endogenous variable fluctuation. The results show that from 1997 to 2014, the quantity of inter-provincial grain virtual water flow increased from 73 billion m3to 124.64 billion m3. The positive driving effect of the population and per capita GDP in virtual water inflow areas is significant, and the negative suppression effect of the grain output per unit in inflow-areas and the population in outflow-areas is significant. Heilongjiang is the province with the largest outflow of virtual water, and the outflow is more sensitive to the shock of local per capita water resources fluctuation. Guangdong is the province with the largest inflow, and the inflow is more sensitive to the local per capita GDP fluctuation. Chinese Mainland's grain virtual water flow pattern and trend will continue to exist in the future. In addition to the endowment of water resources, social and economic factors also need to be considered during the process of water resources management. [ABSTRACT FROM AUTHOR]