Source Data - Y.Z.

China, one of the world’s most water-stressed nations, possesses less than 2,200 m³ of freshwater per capita—around one quarter of the global average. Virtual water, the freshwater embodied in traded goods, offers a means to alleviate scarcity through the import of water-intensive commodities. Here we quantify virtual water flows in grain trade between China and the United States from 1995 to 2022, using crop-specific water coefficients derived from the Penman equation and a logarithmic mean Divisia index decomposition. Our analysis reveals large differences in crop water intensities: Chinese maize and soybean production embody substantially more virtual water, whereas U.S. wheat and sorghum are more water-intensive. China’s virtual water inflow from the United States has increased markedly alongside rapid agricultural trade growth. Between 2014 and 2021, rising product water intensity increased China’s virtual water exports by 1,112 km³, while technological improvements in U.S. agriculture over 2015–2021 significantly reduced its virtual water exports. Optimising China’s grain import composition could yield water-saving potentials exceeding four times the current realised value, underscoring trade’s critical role in mitigating national and global water stress.