Impact of the Three Gorges Dam on flow regime in the middle and lower Yangtze River

摘要

The Three Gorges Dam (TGD) started its regular operation in 2006, and its impacts on flow regime in the middle and lower Yangtze River are receiving attention worldwide. Based on daily river discharge data of seven gauges, flow regime changes in the middle and lower Yangtze River between the pre- and post-TGD periods have been investigated. Water storage by TGD has been found to have significantly reduced the mean flow in October. At the same time, the decrease of discharge from the Dongting and Poyang lakes due to climate variability has also significantly aggravated the reduction of river discharge. According to estimates, the river discharge at the Datong gauge during the TGD impoundment period decreased by 18-40% after the reservoir started full-capacity operations in 2008, at which time TGD contributed nearly 8-18% of this flow reduction. By contrast, the water release by TGD significantly increased the river discharge in February. Meanwhile, TGD changed the magnitude of extreme flows, leading to increase of annual minimum flows and reduction of annual maximum flows. Close attention needs to be given to the possible consequences of TGD-induced flow regime changes in the complex river-lake ecosystem in the middle and downstream sections of the Yangtze River in the future.