Efficiency and sustainability of inter-provincial crop-related virtual water transfers in China

Abstract

The phenomenon of virtual water flows (VWFs) reveals the remote pressure on local water resources on one hand, and provides the possibility of global water saving if VWFs from water-rich places of higher water use efficiencies to water-poor or lower water use efficiencies regions on the other hand. A VWF is marked as efficient when at least half of the water footprint (WF) in producing the traded products is below the corresponding WF benchmark. Whereas the VWF is marked as sustainable when flowing from the places where the water consumption did not exceed local sustainable renewable water availability. However, most attention has been taken to the sustainability of VWFs, ignoring their efficiency and spatial-temporal variations. Here we, taking inter-provincial crop-related VWFs of twenty major crops in the mainland China over 2004–2013 as a study case, analysing the efficiency of VWFs and the sustainability of blue VWFs, as well as their mutual relationship. Results show that over the study period, although inter-provincial crop-related VWFs increased slightly by 2%, the North to South VWFs and blue VWFs increased by 41% and 2.5 times, respectively. The weight of inefficient inter-provincial VWFs reduced to 75% in 2013 from 94% in 2004, whereas the unsustainable blue VWFs increased by 8%. Trade-offs between the efficiency and sustainability of VWFs existed in five provinces. Wheat, rice, maize, and cotton were the main contributors to inefficient and unsustainable VWFs. Assessments in VWFs should account for local water resources conditions, considering both efficiency and sustainability to determine hotspots and critical products and allow appropriate management of crop production and water allocation.