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Background The disproportionate distribution of arable land and water resources has become a bottleneck for guaranteeing food security in China. Virtual water and virtual water trade theory have provided a potential solution to improve water resources management in agriculture and alleviate water crises in water-scarce regions. The present study evaluates the green and blue virtual water content of wheat, maize and rice at the regional scale in China. It then assesses the water-saving benefits of virtual water flows related to the transfer of the three crops between regions. Results The national average virtual water content of wheat, maize and rice were 1071 m3 per ton (50.98% green water, 49.02% blue water ), 830 m3 per ton (76.27% green water, 23.73% blue water) and 1294 m3 per ton (61.90% green water, 38.10% blue water), respectively. With the regional transfer of wheat, maize and rice, virtual water flows reached 30.08 Gm3 (59.91% green water, 40.09% blue water). Meanwhile, China saved 11.47 Gm3 green water, while it consumed 7.84 Gm3 more blue water than with a no-grain transfer scenario in 2009. Conclusion In order to guarantee food security in China, the government should improve water productivity (reduce virtual water content of crops) during the grain production process. Meanwhile, under the preconditions of economic feasibility and land-water resources availability, China should guarantee the grain-sown area in southern regions for taking full advantage of green water resources and to alleviate the pressure on water resources. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]