Three Gorges Project (TGP)

It was during the fifth session of the Seventh National People's Congress that the examination and debate on the feasibility of the Project which lasted more than half a century came to an end and a new era to harness and develop the Yangtze was ushered in. The project will not only make contributions to the present age but also benefit the nation and people for centuries to come.

From its source to its estuary, the Yangtze River meanders over 6,300 kilometers. Its annual runoff into the sea amounts to nearly 1,000 billion m3 and its total drop is more than 5,800 meters with a hydroelectric power potential of up to 268 million kW. In order to harness the River and develop its resources, extensive efforts in survey, planning and scientific research have been made since the founding of the People's Republic of China. After overall planning, repeated studies and verifications, the conclusion has been reached that the TGP is the key to the comprehensive control of the floods and exploitation of the resources of the River.

From Fengjie County to Yichang City, a 200-kilometer- long stretch of the River, it rushes through the majestic Qutang, Wuxia and Xiling gorges, after which the Yangtze Three Gorges is so called . The TGP, which is attracting worldwide attention now, is located at the town of Sandouping, Yichang, Hubei Province in the middle section of Xiling Gorge, about 38 km upstream of the Gezhouba Project. The dam site boasts excellent natural conditions such as a rather wide valley, sound and intact granite bedrock, an average annual runoff of about 500 billion m3 and a vast drainage basin of more than 1 million km2. Decades of arduous reconnaissance and studies resulted in the final approval of Sandouping to be the site of the TGP.

The TGP will be built in accordance with the scheme of "development in one cascade, construction at one stroke, impoundment at stages and resettlement in succession". The concrete gravity dam will be 3,035 m long on the top, with the crest at EL 185 meters. The designed normal pool level of the reservoir is EL 185 meters, and the total storage capacity 39.3 billion m3 , of which 22.15 billion m3 is for flood control. The silt flushing bays are to be arranged in the concrete gravity dam and at the bottom of the power station, with a silt flushing capacity of 2,460 m3 per second. The discharging capacity of the spillway which constitutes the middle section if the dam is 110,000 m3 per second. The designed two powerhouses to be located on both sides of the spillway have 26 units of generators of 700,000 kW each, with a total capacity of 18.2 million kW and an annual output of nearly 84. 7 billion kWh. The designed one-way shipping capacity of the navigation facilities (including a twin 5-step shiplocks and a one- step vertical shiplift) is 50 million tons a year.The shiplocks can adequately handle tows up to 10 ,000 tons and the shiplift can provide immediate service for any vessels under 3,000 tons. The major work amounts of the Project are as the principal indices in Table attached.

It is expected that the preparation work and the main works of the Project will take 2 years and 15 years respectively. By the ninth year the permanent shiplocks and the first group of units will be put into operation. Owing to the construction of the Project, 1.13 million people are expected to be resettled and 28,800 ha. of farmland inundated.

- Main Functions & Project Layout
According to " The Comprehensive Utilization Planning of the Yangtze Basin" approved by the State Council, the Three Gorges Project is the key backbone project for rehabilitation and development of the Yangtze River. The main tasks of TGP are: regulating the floods from the upstream reaches in Sichuan Province to control the floods or relief the flood damage in middle and lower reaches of the Yangtze, especially in the Jinjiang reaches; developing the hydro-power resources in the Three Gorges reach to provide the central China, east China and the east Sichuan Province (now the city of Chongqing, the same as below) with huge amount of the electricity; improving the navigation condition of the reaches between Chongqing and Yichang.

- FLOOD CONTROL

The plain areas along the middle and lower reaches of the Yangtze boast highly developed industry and agriculture. Nevertheless these areas are most vulnerable to floods and waterlogging, because the flood level can be 6-17 meters higher than the ground level of the adjacent plains and they are protected only by the 33,000- kilometer- long dykes . Flooding has been very frequent since ancient times and the reoccurence interval is about 10 years. This is easy to understand because the flood-discharging capacity of the river channel from Jingjiang to Wuhan,which is only 60,000-70,000 m/s,is far too small to discharge the large floods as high as 110,000 m/s. The Three Gorges Dam(TGD)can protect the downstream plain against the biggest flood in 100 years and prevent devastating disasters from occurring in case of the biggest flood in 1000 years,with the help of the flood diversion structure.To avoid heavy losses caused by a possible war, we can prelower the water level, because modern wars always have signs. History will prove the project is the "Patron Saint" ensuring the safety of lives and properties of more than 15 million people inhabiting the downstream areas and 1.53 million ha. farmland as well as the Beijing -Guangzhou and Beijing-Jiulong railroads.

- POWER GENERATION

After completion,the Yangtze River water will be used to produce electricity first at Three Gorges Power Station(TGPS) then regulated by the Gezhouba Project for the purpose of navigation and finally reused for power generation at the Gezhouba Power Station. Thus the total annual output of the two stations is expected to reach 195 billion kwh .When completed,the power output will generate a yearly net value of 10 .5 billion yuan($ 1. 2billion) on the assumption that the price of electricity is 0.1 yuan ($0.0114)per kwh, and an output value of 525 billion yuan($60.3billion)on the assumption that 1 kwh of electricity can produce an output value of 5 yuan ($0.57),which can result in job opportunities for nearly 5.25 million people assuming that a yearly value of 10,000 yuan($1,149)can be created per person.It should also be noted that the Project enjoys a very advantageous geographical position ,being within 1,000 km of many industrial centers.it is expected to be the network junction for graphical position,being within 1, 000 km of many industrial centers.It is expected to be the network junction for all the power grids in the country.When the grid goes into operation, it will not only supplement the available thermal power, hydro-power and nuclear power in the country, but also upgrade the quality and efficiency of the grid, which will certainly make the Project the national nerve centre-the electricity dispatching centre.

- NAVIGATION IMPROVEMENT

At present,the 660 km waterway between Chongqing and Yichang cuts through hills and mountain gorges with a 120-meter drop and 139 dangerous shoals and rapids,46 one- way sections, 25 locations where large fully-loaded freighters need winching and the annual one- way shipping capacity is less than 10 million tons. The completion of the project will substantially improve the navigation conditions on the river above the dam,with the navigation channel broadened to an average of 1,100 meters,enabling 10, 000 tons to sail all the way from Shanghai to Chongqing.This improvement can lead to an annual increase in one-way shipping capacity to 50 million tons and a cut in the shipping cost by 37‰ ,creating conditions for boosting the economy of the Southwest,Central as well as East China.

- Aquaculture

The 175-meter-high dam will help to form a huge reservoir of 1,150 km .Apart from waterway,there is still 700km of water surface. The flow velocity will be slower and the water will be clearer, more nutritious and warmer in the surface layer,which will make a vast fresh water aquaculture base for raising shrimps. shellfish,fishes,geese,ducks and crabs.Consequently,the formation of the reservoir will result in rapid development of agriculture, forestry, animal husbandry, sideline production as well as fishery on both banks of the reservoir.

After completion,the water level behind the dam will be raised by 110 meters.Though some scenic spots and places of historical interests such as QuYuan Temple, Zhang Fei Temple and several sites or stone inscription will be submerged,the scenery on the whole will remain as magnificent,unique and mysterious as ever. Besides, careful plans have been made to remove or rebuild the ones to be submerged. The mountains that flank Qutang Gorge and Wuxia Gorge, for example, reach more than 1,000 meters above sea level, and the water level enhancement there will only be about 38-46 meters respectively.The formation of the artificial lakes among spectacular mountains will only add to the beauty of the Three Gorges because a lot of of new scenic spots will turn up and dozens of scenic spots scattered along the Three Gorges will be more easily accessible. These include the Dazu Stone Sculpture, the Gaolan scenic area covered with an ocean of pine tress,the Minor Three Gorges along the Daning River, Shennongjia nature reserve, Shennong Brook, Gezi River Stone Forest as well as the two modern wonders-the Gezhouba Dam and the Three Gorges Dam.That's why the future Three Gorges, a combination of natural beauty,ancient cultural relics and historical sites as well as modern miracles,will intoxicate travellers from all over the world.

- Development-oriented resettlement

From 1985 to 1993, the government invested 1. 2 billion yuan( $ 137 million)for experimental settlement in the pilot areas. These include 14,000 ha.of newly opened and improved terraced fields, 1500 items of construction of buildings, houses, bridges, roads and water supply projects for resettlement,and the resettlement of 30,000 migrants and 100 factors.All these projects have already achieved tangible economic returns and are well received by the settlers.Valuable experiences have fully proved that the development-oriented policy provides a very good opportunity for the settlers to free themselves from poverty.That's why the construction of the Project has brought about a once- in- the- blue -moon opportunity for economic boom for the regions around the reservoir.

- Transferring water from the south to the north

The annual runoff of the Yangtze River into the sea is 23 times more than that of the yellow River.It is estimated that the total volume of water to be consumed in the Yangtze valley after the year 2000 will be approximately 210 billion m3 a year , and about half of it can be recycled.However North China,especially Beijing suffered several severe water shortages.In 1981, the water crisis forced the thermal power plants to stop operation,which resulted in industry shortages. which resulted in industry losses of about 2 billion yuan ( $ 229 million).It is very common that high buildings have inadequate water supply,but on the other hand,luxury hotels are mushrooming.To alleviate this intense situation,Beijing has to get water supply from Guanting and Miyun reservoirs which were originally planned mainly for agriculture irrigation. It is estimated that the amount of water shortage each year in Beijing, Zhengzhou and several other northern cities after the year 2000 total 40 billion m3.The rise to 175 meters of the Danjiangkou Dam,which is the source for transferring water from the South to the North,can only bring the water transfer volume up to 23 billion m3.What is the way out? The Yangtze Three Gorges Project .After the completion of the TGP,by taking advantage of the time between 0:00 to 6:00am,when power transmission load is sharply released, the water lever of the TGD will be raised by a dozen meters with water from Xiangxi River,a tributary in the backwater area,enabling the water to run through Shenlongjia to the Danjiangkou Reservoir and further through Henan,Hebei Provinces and then finally to Beijing and Tianjin ,consequently,alleviating the water shortage in these areas. The above facts show the transferring water from the South to the North can not only relieve the water shortage in the North, but also reduce the transportation pressure and high demand for farmland caused by transferring coal from the South to the North. It's of great immediate and historical significance for ecological protection and reducing pollution.

- Water Supply and Irrigation

As we know, the North China plain makes up 40% of China's cultivated land, but its river runoff takes up only 6.5% of the country's total. In the recent few decades, North China has been developing very rapidly in industry, agriculture, business, trade, science and tourism. All these, together with the population explosion have made water crisis in these areas worse than ever.Many rivers such as Shaying River, Daqing River and Ziya River which used to be very highly developed in navigation are no longer suitable for navigation now. The famous Baiyangdian Lake has dried up several times and even the Yellow River nearly dried up in 1992. For water supply and irrigation, the limited underground water has been overextracted and this is after all an utterly inadequate measure. Water is vital to these areas because these are important production areas of grain and cotton in China. The estimated annual shortage of water in these areas is about 70 billion m3. The only way to alleviate the pressing needs is to build the TGP. Further extension of the transferring canal from Beijing to the Han River will enable the water of the Yangtze to flow to the North. Thus the thirsty land can get watered and the fertile land of China will overflow even more fresh with powerful vigor.

- Project Layout and Hydraulic Structures

- Dam Site

After repeated study and analysis on 15 dam site alternatives, the dam site of the TGP is finally selected at Sandouping with the crystalline rock as its foundation. The total water catchment layout of the Three Gorges project area hereof is about one million km2 with 451 billion m3 of average annual runoff and 530 million tons of annual sediment discharge.

Here at the location of Sandouping dam site, the river valley is relatively open and broad, the mountains on both sides of the river are fairly flat with a small islet called Zhongbaodao in the river, which is favourable for river diversion scheme with phased construction. As for the outside communications nearby, there exists a railway to Yichang, with a distance of 40 km to the dam site and a high standard express from Yichang to the dam site, and a bridge on the Yangtze River has been constructed and was open to traffic in 1996. Besides, there are direct accesses by a standard highway and waterway to the dam site.

The bedrock of the dam site is sound and intact granite with 100 MPa of comprersive strength. The faults and fissures in the bedrock are less developed and most of them are very well cemented. And the permeability of the rock mass is slight in nature. The weathered layers in the hills on both sides are a bit thick, ranging from 20 to 40 m, while few layers exist on the main river channel.

In the vicinity of about 15 km around the dam site, there are no major disadvantageous geologic structures. The regional seismic activities are small in intensity, low in frequency. Therefore, the whole area belongs to a slight seismic area ranking as 6 degree of seismic intensity classified by the state authority department concerned.

- Layout of the Project
The The project is composed of a dam, two power plants and navigation facilities. For a long time, efforts were engaged in the in-depth study and research on various schemes to determine the structural pattern, configuration and layout of the structures. And it was not until undergoing analysis by scientific researches and tests regarding hydraulics, sedimentation, structure and material, etc. , that these issues were finally determined. The overall layout of the project is as the following.

The spillway is placed in the center of the river bed, i. e. , on the original main river course, while the intake dam sections and non-overflow dam sections are arranged on its both sides. The power plants are placed on the back of the intake dam, and in addition, an underground power plant on the right bank is to be built in future. The permanent navigation structures are located on the left bank side.

- Dam
The dam is of a concrete gravity type. The total length of the dam axis is 2,309.47m, with the crest elevation at 185 m and a maximum height of 175 m.

The spillway section, which is located in the middle of the river course, is 483 m long in total. In this section, there are 23 bottom outlets and 22 surface sluice gates. The dimensions of the bottom outlets are 7 * 9 m, with the elevation of the inlets at 90 m. The net width of the surface sluice gates is 8 m, with its sill elevation at 158 m. In the downstream part of this section, flip bucket for energy dissipation is provided.

On both sides of this section, there will be arranged the intake - dam and non- overflow dam sections.

The maximum discharge capacity of the Project can reach 116,000 m3/s, which is able to discharge the possible maximum flood.

- Power Stations

According to the scheme, two power plants will be placed at the toe of the dam, one on each side. The total length of the power plant on the left is about 643.6 m, with 14 sets of turbine generator units installed, while that of the one on the right , 584.2 m in total length, 12 turbine generator units installed. Thus, there are 26 sets of turbine generator units in total (the turbine is of Francis type) , 700 MW for each, totaling 18,200 MW in installed capacity that will produce 84.68 TW/h of electricity output annually. 500 kV AC transmission lines will send electricity to Central China and the east of Sichuan Province. 600 kV DC transmission lines will send the electricity to East China. There are 15 transmission lines in total.

On the right bank, enough room has been preserved for the future underground power plant with 6 turbine generator units, 4,200 MW of installed capacity. The intakes will be constructed simultaneously with the project.

- Navigation Facilities

The permanent navigation structures consist of the permanent shiplocks and a shiplift.

The shiplocks are schemed out as a double - way and five - step locks, each lock chamber is dimensioned at 280*34*5 m(i.e. length * width * water depth) capable of passing 10,000 tons of barge fleet.

The shiplift is designed as one stage vertical hoisting type. The ship container of the shiplift is in a size of 120*18*3.5 m, capable of carrying one 3,000 tons of passenger or cargo ship each time.

In addition, one temporary shiplock is schemed for use during the construction period with an effective chamber size of 240*24*4 m.