The Characteristics and Evolution of Structural and Functional Connectivity in a Large Catchment (Poyang Lake) during the Past 30 Years

Hydrological connectivity plays a major role in solving water resource and eco-environmental problems. However, this phenomenon has not been afforded the attention it deserves. The detailed analysis of connectivity in river systems could provide considerable insight into the structural and functional attributes of riverine landscapes. The current study used a graph theory approach and associated connectivity indicators to explore the characteristics and evolution of river systems and hydrological connectivity in a large catchment (Poyang Lake, China). The results revealed that the structure of the river system tended to be complex during 1990-2020, characterized by a dynamic evolution of tributaries in certain northern areas. Both river density and complexity exhibited an increasing trend by up to 15%, with the change rate after 2000 approximately twice as high as that of the preceding period. Overall, human activities across the catchment were more likely to play a key role in leading to significant changes in the quantity, morphometric, and structural characteristics of the river system. Additionally, the functional connectivity analysis indicated that the index of connectivity (IC) in the downstream catchment was stronger than that of the upstream vegetation areas, suggesting a strong contribution to the runoff sediment transport (r = 0.6-0.7). This study highlights the spatial and temporal evolution of both structural and functional connectivity in the large Poyang Lake catchment. The findings of this work will benefit future water resource management and applications by providing a strategy for protecting the surface hydrology and mass transport of large river basins under climate and land use changes.

Automated summary

Hydrological connectivity is crucial for addressing water resource and eco-environmental issues. This study used a graph theory approach to analyze the connectivity of river systems in the Poyang Lake catchment. The results indicated a complex structure and evolving tributaries in certain areas. Human activities were found to significantly impact the quantity, morphometric, and structural characteristics of the river system. Functional connectivity analysis revealed that downstream areas had stronger connectivity and played a crucial role in runoff sediment transport. This study provides insights into the spatial and temporal evolution of connectivity in a large river basin and offers strategies for water resource management under climate and land use changes.