Information-theoretic insights into river-tide connectivity in the Pearl River Delta: Implications for complex network dynamics

The Pearl River Delta (PRD) is among the world’s most intricate delta systems, shaped by the dynamic interaction of upstream runoff and downstream tidal dynamics. However, the mechanisms underlying river-tide connectivity within such complex networks remains insufficiently understood, particularly the nonlinear feedback loops and spatiotemporal lag effects governing water level dynamics. This study employs an information-theoretic framework to investigate water level connectivity in the PRD, integrating relative mutual information (RMI) and relative transfer entropy (RTE) to quantify synchrony, causality, and directional information flow among hydrological variables. Results highlight the dominant role of upstream river discharge on water level synchrony in the Xijiang and Beijiang River systems, while downstream tidal dynamics exert greater causal effects in the Pearl River’s mainstream and coastal distributary regions. Since the 1990s, human activities, such as dam construction and channel dredging, have attenuated the influence of river discharge while leaving tidal impacts largely unchanged. Seasonal analysis reveals that that upstream river discharge predominantly governs water level connectivity during the flood season, whereas downstream tidal forcing becomes more prominent in the dry season, with spring tides amplifying these effects across both seasons. The study further shows spatiotemporal heterogeneity in connectivity, highlighting nonlinear feedback mechanisms and lag effects across subsystems. These insights underscore the adaptability and resilience of the PRD under both natural and anthropogenic pressures. By providing a novel perspective on deltaic process dynamics, this study contributes to the theoretical foundation for sustainable management and resilience planning in the PRD.