Climate change, human activities, and the mid-nineteenth century evolution of the Jingjiang river channel in the Yangtze river's middle reaches

The Yangtze River is the longest and one of the most important rivers in Asia. The channel diversion event of the Jingjiang River section in the Yangtze River's middle reaches in the mid-nineteenth century was a critical episode in the evolution of the Yangtze River's middle reaches. This study uses historical records to reconstruct a sequence of dry-wet variations in the upper and middle reaches of the Yangtze River in the period since 1500. The results show that 1820–1870 was the wettest period in the middle and upper reaches of the Yangtze River. Climate change played a critical role in this abrupt transformation. Increased precipitation resulted in an increase in sediment from the upper reaches, accelerating sediment deposition and riverbed elevation. Frequent flooding events directly led to this event. This process was intertwined with the long-term impacts of human activities such as levee construction, land reclamation, soil erosion and water loss, as well as government decisions regarding river management at the time. This study summarizes the mechanisms by which the interplay between climate change and human activities affects large river systems in historical period. The research findings provide a reference for natural and social systems in historical periods to adjust to climate change impacts.