The middle route of the south-to-north water diversion project and urban ecological welfare performance: Evidence from water-receiving cities

The implementation of the Middle Route of the South-to-North Water Diversion Project (MRP) has effectively alleviated the severe water shortage in northern China; however, whether and how it produces synergistic effects on the ecological, economic, and social systems of the water-receiving areas remains a key issue requiring in-depth assessment. Using panel data from prefecture-level cities for the period 2006–2023, this study estimates urban ecological welfare performance (EWP) via a global super-efficiency SBM model (GS-SBM). On this basis, the difference-in-differences method is adopted to examine the implementation effects and mechanisms of the Middle Route Project. The results indicate that: (1) The project is significantly correlated with improvements in urban ecological welfare performance in the water-receiving areas; this conclusion remains valid after robustness tests, including the parallel trends test. (2) The results of the mechanism analysis suggest that industrial structure upgrading, technological progress, and human capital accumulation may be potential channels through which the project influences the ecological welfare performance of water-receiving cities. (3) The policy effects are more pronounced in cities with higher administrative levels and higher levels of economic development, whilst they are not yet significant in areas where groundwater over-abstraction is particularly severe. These findings provide empirical evidence at the city level on the relationship between the Middle Route of the South-to-North Water Diversion Project and the ecological welfare performance of water-receiving cities, and offer a theoretical basis for China's ecological civilisation construction and decision-making on cross-regional resource allocation.