Assessing the real impact of inter-provincial grain trade on water and land resources within China via a modified framework

A rational evaluation of the 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 resource 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 irrigation’s marginal productivity enhancement effect under cropland constraints. Applied to empirical analyses of interprovincial grain transfers within China, where arable land resources are strictly constrained, a modified framework was developed to incorporate irrigation effects into virtual water and land resource accounting. China's land and water productivity under irrigated agriculture is 2.18- and 1.32-fold greater than under rainfed agriculture, respectively. However, the irrigation provision rate is less than 50 %. From 2005–2015, interprovincial virtual water flows increased from 45.94 × 109 m³ to 98.80 × 109 m³ , and virtual land flows increased from 3.64 × 106 ha to 9.35 × 106 ha. A benefits evaluation showed that, over the same period, virtual water wastage decreased from 8.24 × 109 m³ to 3.79 × 109 m³ , and virtual land wastage increased from 1.81 × 106 ha to 4.22 × 106 ha. Therefore, failure to consider the role of irrigation can lead to erroneous grain virtual water and land trade evaluations. In altering the perspective of virtual water and land resource assessment, this study provides a basis for agricultural layout optimisation, irrigation development and water resource management policies.