How centralizing environmental enforcement affects water quality: A quasi-experiment in China

China is ambitiously promoting centralization reform as a panacea for strict environmental regulation and pollution control. Numerous publications have confirmed the positive impacts of this reform on air quality and climate change. However, the impacts of centralization, particularly the centralization of environmental enforcement, on surface water quality remain unclear. To address this gap, this paper collected data from 78 surface water quality monitoring stations in China between July 2018 and December 2020 and used comprehensive administrative enforcement reform for ecological and environmental protection in China as a quasi-experiment of environmental enforcement centralization. The results of the staggered difference-in-differences estimation show that comprehensive administrative enforcement reform does not significantly improve integrated water quality, dissolved oxygen, permanganate index, and ammonia nitrogen. Its positive impact is confined to improving the acidity and alkalinity of surface water. Heterogeneous analysis reveals that comprehensive administrative enforcement reform has caused a significant deterioration of boundary water quality. However, comprehensive administrative enforcement reform can significantly improve integrated water quality if the mayor of the city where the monitoring station is located is older than 55. This demonstrates that local governments may control water pollution selectively due to economic costs and promotion motivations. This paper provides new insights into environmental centralization and water pollution control via data from China. Based on these findings, we recommend that global policymakers prudently expand the application scope of environmental centralization, focus on trans-border pollution, and design scientific cadre performance evaluation systems.