The impact of the river chief system on transboundary water pollution

The River Chief System (RCS) in China plays a crucial role in addressing transboundary water pollution (TWP), which is vital for achieving the Sustainable Development Goal of "clean water." This study examines the static and dynamic effects of the RCS on TWP using a difference-in-difference-in-differences (DDD) model and manually collected RCS data from 104 counties between 2007 and 2020. The results show that the RCS significantly reduces chemical oxygen demand (COD) by 15.9% and ammonia nitrogen (NH₃-N) by 22.9% in border counties, though it has no notable impact on dissolved oxygen (DO). Additionally, RCS intensity contributes to a 13.8% reduction in COD. However, no sustained dynamic effects are observed for COD or NH₃-N reduction over time. Several robustness checks confirm the validity of these findings. Heterogeneity analysis indicates that the RCS's impact is more pronounced in counties with higher economic development, upstream locations, lower initial pollution levels, and younger local government leaders. This study not only provides critical insights for water resource management in China but also offers international relevance for addressing TWP governance challenges in transboundary water bodies.