Assessing the Real Impact of Inter-provincial Grain Trade on Water and Land Resources in China: A Modified Framework Incorporating Irrigation Productivity

A rational evaluation of virtual land and water resource flows within the grain trade can potentially serve: (i) to mitigate regional resource scarcity, (ii) as the basis for agricultural water and land resource management, and (iii) to support policymakers in making strategic choices for resource redistribution and sustainable development. Failing to reflect real-world agricultural production systems and irrigation-driven resource management practices, existing evaluation frameworks consider only the virtual water and land content embedded in traded grain, neglecting the marginal productivity enhancement effect of irrigation under cropland constraints. In this study, a modified framework was developed to incorporate irrigation effects into virtual water and land resource accounting and was applied to an empirical analysis of interprovincial grain transfers in China, where arable land resources are strictly constrained. The results indicate that China's land and water productivity under irrigated agriculture are 2.18- and 1.32-fold greater than under rainfed agriculture, respectively; however, the irrigation provision rate remains below 50%. Failure to consider the role of irrigation leads to contradictory evaluation results for virtual water and land flows in certain trade routes, thereby generating misleading policies. Aiming at the 2030 grain production target, this study further explores the feasibility of boosting grain production capacity by expanding irrigation coverage using water resources saved through efficiency improvements. Furthermore, the modified trade framework is utilized to identify optimal pathways for interprovincial production increases. By altering the perspective of virtual water and land resource assessment, this study provides a basis for agricultural layout optimization, irrigation development, and water resource management policies.