Connectivity of Complex River Networks with Multi-Hub Cross-Basin Water Diversion: A Case Study of the Yangtze River–Taihu Lake Transfer Scheme

A cross-basin water diversion project, as a method to manage water resources, regulates the operation modes of key hubs (e.g., pumping stations and gate complexes) and selectively enhances, weakens, or reconfigures the water flow paths within the region, thereby substantially altering the hydrological connectivity pattern. In particular, within complex river networks, the underlying mechanisms and quantitative relationships through which their operational mode influences longitudinal connectivity changes and subsequently affects regional water distribution remain poorly understood. Using the Yangtze River–Taihu Lake diversion project as a case study, we developed a directional longitudinal connectivity index (DLCI) based on a numerical model and max-flow theorem to analyze water connectivity and allocation under different multihub diversion modes. The results reveal that the DLCI is positively correlated with both the water replacement rate and key hydrodynamic parameters. Spatially, water originating from the Yangtze River propagates along gradients of DLCI, flowing from areas of high connectivity to regions with lower values. The magnitude and distribution of diverted flow were identified as major factors influencing DLCI. Specifically, this study demonstrates that the median DLCI shows a significant positive correlation with the total diverted flow. Moreover, under equivalent total inflow conditions, dispersing flow across multiple gates results in higher median DLCI and improved spatial uniformity compared to concentrating flow through a single gate. At the subregional level, operational gates help maintain hydrodynamic conditions within an optimal range, thereby supporting local connectivity. Based on these findings, we developed a multiple linear regression model relating gate flow rates to objectives and proposed a targeted joint scheduling strategy that accounts for differential flow contributions from each hub. Based on this study, the application of DLCI can provide practical support for the joint operation and management of interbasin water transfer projects.