Influences of the south–to-north water diversion project and virtual water flows on regional water resources considering both water quantity and quality

In this study, a comprehensive water stress indicator was proposed based on the concepts of the blue water footprint and grey water footprint, which can reflect regional water scarcity from the perspectives of both water quantity and quality simultaneously. Additionally, hypothetical water stress was calculated to show the effects of physical water transfer in the South-to-North Water Diversion Project and the virtual water transfer. The results indicated: (1) Physical water flows from Jiangsu and Hubei to Beijing, Tianjin, Hebei, Shandong, and Henan, and the largest virtual water exporters and importers are Henan and Beijing, respectively. (2) Water transfers play a role in alleviating regional water stress in Beijing and Tianjin, and the situation was the opposite for the rest regions. (3) In Hebei, the water stresses related to water quantity and water quality were 0.779 and 0.081, respectively, and significant influence could be seen in Hubei when comparing the water stress levels in actual and hypothetical situations. Physical water transfer has increased water availability in water-importing regions, but it also poses adverse impacts on the ecosystem and environment. Virtual water export leads to greater water consumption, and changes in the production and export patterns from water-intensive products to less water-intensive products should be considered. A comprehensive picture, including both physical and virtual water, is urgently required for sustainable water management, especially for regions like Hubei. Apart from measures to decrease blue water consumption related to product production, a decrease in pollution related to nitrogen application should be encouraged.