China Yangtze Three Gorges Project (TGP), as one of the biggest hydropower-complex project in the world, ranks as the key project for improvement and development of Yangtze River. The dam is located in the areas of Xilingxia gorge, one of the three gorges of the river, which will control a drainage area of 1 million km 2 , with an average annual runoff of 451 billion m³ . The open valley at the dam site, with hard and complete granite as the bedrock, has provided the favorable topographical and geological conditions for dam construction.