Hydrological connectivity research in Lake Taihu Basin: Status, progress and future challenges

Hydrological connectivity, the key bond in the transfer and exchange of material, energy and biological information between rivers and lakes, exerts coupling and feedback effects on the water quality, aquatic ecology and habitat conditions. Thus, it has become a hot spot in the fields of hydrology, hydraulics and ecology. The Lake Taihu Basin is a typical basin with a densely distributed river network in China. Due to rapid urbanisation and the construction of numerous hydraulic facilities in the area, the hydrological connections and interactions between rivers and lakes have been altered at an unprecedented rate, resulting in a series of ecological and environmental problems. In this study, the concept and connotation of hydrological connectivity were introduced based on a literature review, and the research progress of hydrological connectivity in the Lake Taihu Basin was systematically examined. The methods of evaluating hydrological connectivity in the Lake Taihu Basin are mainly based on graph theory, landscape pattern index and hydrological connectivity function, and focus on regional-scale research. According to the intensity of human activities, the evolution process of the river-lake network in the Lake Taihu Basin can be roughly divided into the naturally-formed stage, the ancient human-influenced stage and the modern human-influenced stage. Results showed that, in the past century, changes in the hydrological connectivity of the Lake Taihu Basin were influenced by climate change and human activities, especially human activities caused by water hydraulic facilities and urbanisation. Moreover, desirable hydrological connectivity is beneficial to flood mitigation in flood season and to water resources supply in the non-flood season, whereas the effects of improved hydrological connectivity on water quality and aquatic ecology remain controversial due to the involvement of various factors. Given the current research and existing problems observed in studies devoted to the hydrological connectivity of the Lake Taihu Basin, the prospects for future research are proposed as follows. First, the quantitative characterisation and assessment of hydrological connectivity is a premise for hydrological connectivity research. Second, the quantitative analysis of the driving mechanisms of the hydrological connectivity variations is a challenging topic in the research of hydrological connectivity. Third, tracking the impacts of the large-scale water diversion projects on the hydrological connectivity changes is a long-term task. Moreover, studies on the associated environmental and ecological effects of eco-hydraulic engineering transformation and the multi-objective optimisation of hydrological connectivity regulation in the context of engineering control are the ultimate approaches to achieve the synergetic optimisation of various ecosystem services, such as flood regulation, water supply, water purification, and biodiversity conservation in the Lake Taihu Basin. © 2022 by Journal of Lake Sciences.