Hydrological exchange between the trunk stream and the floodplains is the key factor maintaining ecological functioning. The water discharge diverting from the Yangtze River to the Dongting Lake has recently decreased considerably in China. However, their variation characteristics and major driving factors remained unclear. In this study, Mann Kendall trend and Pettitt abrupt tests were employed to determine the changes of time series. Double mass curve analysis and regression analysis were used for the qualitative analysis of the impacts of climate change and human activity. Results revealed that precipitation change trends significantly decreased in autumn. The water discharge at the trunk Yangtze River had a decreasing trend in autumn and an increasing trend in winter. The annual and seasonal water discharge diverting from the Yangtze River to the Dongting Lake, except at Xinjiangkou in summer, exhibited significant downward trends. No consistent trends in precipitation and water discharge were identified, thereby indicating that the seasonal relationships between them had been disturbed by human activities. Human activities had a dominant effect on the water discharge exchange between them during 1967–2018. Along with the intensification of human activities, the hydrological connectivity between the Yangtze River and the Dongting Lake would probably be further changed in the near future.
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