Effects Of The Three Gorges Reservoir (TGR) Phase-Ⅰ Water Storage On The Yangtze River Sediment

The Three Gorges Project (TGP) on the Yangtze River, the largest hydropower-complex project ever built in the world, completed its Phase-II construction and Phase-I water storage in 2003, finally elevating the pool level to about 135 m above mean sea level at the dam. The potential eco-environmental problems induced by the TGP are widely concerned at home and abroad. Sediment research in particular is one of the most important concerns about the TGP. The Three Gorges Reservoir (TGR) sedimentation will affect the normal operation of the TGR, hydropower generation, and navigation. The Yangtze River sediment entering the sea is closely related to the evolution of the Yangtze River mouth, mouth bar, river delta, and even deposition patterns of the East China Sea. On the other hand, the Yangtze River sediment features are closely related to the particulate geochemical compositions, which have important effects on the estuarine, coastal, and even shelf areas ecosystem and environment. Thus, it is necessary and urgent to examine the effects of the TGR water storage on the Yangtze River sediment, which has important practical and theoretical significance.Supported by the National Basic Research Program of China for Land-Sea interaction and its effect on the environment in the typical estuaries and offshore areas of China (Project No: 2002CB412400), the thesis firstly examined the temporal variability in water and sediment entering oceans by 9 major rivers in China during 1953-2003, including the Yangtze River, Yellow River, Pearl River, Huaihe River, Songhuajiang River, Liaohe River, Qiantangjiang River, Minjiang River, and Haihe River, and further, identified some factors leading to such temporal variability. Secondly, the thesis took the excellent opportunity of the Phase-I water storage of the TGR timely and systematically examined its effects on the sediment of the Yangtze River mainstream, estuary and adjacent seas.The main results in the thesis were drawn as follows:1. Temporal variability in flux of water and sediment entering seas by 9 major rivers in China...