Spatial correlation network characteristics and influencing factors of water environmental efficiency in three major urban agglomerations in the Yangtze River Basin, China

Within the framework of achieving carbon peak and neutrality, studying the measurement and spatial correlation network of water environmental efficiency (WEE) is beneficial for protecting the water environment and strengthening the coordinated development between regions. This study quantifies WEE under carbon emission constraints in three major urban agglomerations in the Yangtze River Basin. Employing a modified gravity model paired with social network analysis (SNA) method, we establish a spatial correlation network. Furthermore, we explore the determinants of the spatial correlation network using Quadratic Assignment Procedure (QAP) model. The research findings indicate that: (1) WEE exhibits fluctuations and increases, illustrating a trend of 'high on both sides and low in the middle.' (2) The spatial connection of WEE is tightening, demonstrating significant spatial spillover effects. Compared to Chengdu-Chongqing and the Midstream, the Yangtze River Delta has transitioned from a 'dual-core' setup to a multicentric network, which is more stable and showcases tighter interconnections. (3) Urbanization, population density, industrial transformation, and technological innovation emerge as the primary influencing factors of the spatial correlation network, displaying both temporal and regional heterogeneity. This study provides a theoretical framework and empirical support for water environmental protection and offers insights for policy-making towards green sustainable development.