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the area in the middle and lower reaches of the Yangtze River. Its favorable geographical location make it possible to effectively control the huge flood water from the upstream of the Yangtze. With a 22.15 billion m3 of flood control storage capacity of the reservoir, the flood control capability of the Jingjiang River section, the most critical section in flood control, would be able to be improve from the present 10--year frequency flood to the 100--year. Even should a 1, 000¡ª¡ªyear frequency over flood occur, the vast plains on both sides of this river section, with the regulation of TGP and with the assistance of appropriate operation of the flood diversion and retention works, would be kept from destruction which might occur due to breaching of the main levee along the section without TGP. The flood disaster in the area of the middle and lower reaches of the Yangtze and the threat of flooding to Wuhan City would be mitigated. And so would it create favorable conditions for a thorough rehabilitation and improvement of the Dongting Lake area. 1.2 Power Generation Being provided with a total installation of generating capacity of 18, 200 MW, and with an average annual output of 84.68 TW¡¤h, TGP will supply a large proportion of its electricity to East China, Central China and a small proportion to the east Sichuan province and Chongqing Municipality. This means a replacement of 40 to 50 million tons of raw coal combustion each year. And this reliable, cheap and renewable energy will play a very important role in the development of economy and the prevention of environment al pollution. 1.3 Navigation Improvement The 660km long waterway from Yichang City to Chongqing Municipality will obviously be improved after the completion of the TGP reservoir, making it possible for 10, 000 tons of barge fleet to sail upstream directly to the harbour of Chongqing. Thus, an increase of annual one-way navigation capacity from present 10 million tons to 50 million tons, and a decrease of the navigation cost from 35 % to 37 % will be reached. With the regulation of the reservoir, the minimum flow downstream of Yichang in the dry season will be increased from the present 3,000 m3/s to over 5, 000 m3/s, which will obviously improve the navigation condition in the dry season in the middle reaches of the Yangtze River. 1.4 Miscellaneous The project will, for certain, promote the development of fishery in the reservoir, as well as tourism and recreational activities. It will evidently improve the water quality of the middle and lower reaches of the river during the dry season and create favorable conditions for the South-to-North Water Transfer.
Site in 2009 2. PROJECT LAYOUT AND MAIN HYDRAULIC
STRUCTURES 2.1 Dam Site After repeated study and analysis on 15 dam site alternatives, the dam site for TGP is finally selected at Sandouping with the crystalline rock as its foundation. The total water catchment area hereof is about one million km2 with 451 billion m3 of average annual runoff and 526 million tons of annual sediment discharge. Here at the location of Sandouping dam site, the river valley is relatively open and broad, while the
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