Feeding today, thirsting tomorrow? China’s food security responsibility and unsustainable water use

Using county-level designation as major grain-producing counties to capture China’s food security responsibility (FSR), we examine its impacts on water sustainability. Our findings are three-fold: (1) FSR significantly reduces terrestrial water storage (TWS) and groundwater storage (GWS); (2) Heterogeneous effects are stronger in main grain areas, become more pronounced after the Food Security Governor Responsibility System Evaluation (FSGRSE), are more significant where TWS and GWS decline is more severe, and amplify under low-precipitation conditions; (3) Further analysis shows irrigation expansion is the mediating channel from FSR to TWS and GWS decline, with a stronger mediation effect in fiscally constrained counties. These results suggest that the institutional design of FSR induces unsustainable water use, highlighting a trade-off between “feeding today” and “thirsting tomorrow.”