Effect of the Three Gorges Dam and other upstream factors on the hydrological conditions of Yichang reach, Yangtze River

Human activities in the upper stream of Yangtze river, especially the Three Gorges dam built in 2003, have drastically changed its upstream flow and sediment transport. In this study, long-term hydrological process in both upper & middle Yangtze river and their relationships were quantitively analyzed. At first, the hydrological variation at the inlet of middle Yangtze river were calculated. Results showed that the sediment reduction is of the most importance to the middle stream. Then the influence of Three Gorges dam and other upstream factors were estimated respectively according to a detailed study on channel erosion/sedimentation. About 40% of the total sediment reduction in the middle stream was caused by the Three Gorges dam. And the main upper tributaries’ reservoirs which were built in past decades contributed about 25% sediment reduction. Contributions of different tributaries and the variation tendency were also discussed in this paper.