The Three Gorges Project. Part I: What is TGP?
The Yangtze River starts the journey from the Roof of the world -
the Tibetan Plateau (Qing Zhang Gao Yuan), which is a northwestern
mountainous area with an elevation of more than 4,500 meters. The tremendous
potential sustains its restless flow through 10 provinces across China, joining
more than a thousand tributaries on its way to the East China Sea, where it
finally enters the Pacific Ocean. The whole river, 6,300 kilometers long, can
be divided into several streches. The following description of the Yangtze is
for those who are not very familiar with the river. A detailed map of China
will make everything easier and is highly recommended [1].
The upper reach of the Yangtze, some 4,530 kilometers long, runs
from the northwestern province Qinghai (the Green Sea) to Yichang, a city
with a large hydrometric station in Hubei (which implies "the north of the
lakes" in Chinese). The upper reach includes the Jinsha Jiang (the Golden
Sand River, where Jiang=river) and the Chuan Jiang. The Jinsha Jiang, from
Zhimenda of Qinghai to Yibin of Sichuan, is a narrow river which takes up a
half drop of the river. The Chuan Jiang then flows through a large part of
Sichuan Province. It joins the Jialing Jiang at the industrial port city
Chongqing and the Wu Jiang at Fuling. Both rivers are the major tributaries
of the Yangtze. It then enters Hubei, a province used to be famous for being
the hometown of a thousand lakes. As the river gains a broader width, the
Chuan Jiang flows much slower than the Jinsha Jiang. It reaches Yichang,
where the recently finished Gezhouba project, the largest dam so far in the
history of the People's Republic, is located. The beautiful Three Gorges
(Sanxia), 195 Km long, is from Fengjie in Sichuan to Yichang in Hubei. There
the channel is only 200 meters wide and sheer walls rise 500-600
kilometers above the river. The Three Gorges Dam is proposed to be built at
Sandouping, a small village only 40 Km upstream from the Gezhouba project.
Table I. The mainstream of the Yangtze River [2].
River/reaches Length (Km) Width (m) Drop (m)
Jinsha Jiang 2,308 10-100 > 3,000
Chuan Jiang 2,222 300-800 1,500
Middle & lower 1780 > 1000 40-50
Total 6300 6,600
Every year, the Yangtze carries an average of 979.4 billion cubic
meters of water to the Pacific ocean. The per annum flow at the estuary
reaches 31,060 cubic meters per second.
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The middle reach of the Yangtze flows through most part of Hubei.
The stretch of the river below Yichang is called the Jing Jiang, which, due to
serious siltation of the river bed, is considered to be the most dangerous
flooding area of the whole river. The 182-Km-long Jingjiang Dyke (Jingjiang
Da Di) has been keeping the turbulent water from flooding during the
summer and fall seasons every year. Further downstream are the Four
Lakes area (all in Hubei) and Lake Dongting (Dongting Hu, where Hu=lake),
which is the second largest lake in China and is mostly located in Hunan
(implying "the south of the lakes" in Chinese). Due to the abundant rain fall
in this plain area, flood is often a threat to the large amount of farmland
near the river coast. About 700 kilometers downstream of Yichang is the
large industrial city Wuhan, where the Han Shui (Shui=river), another major
tributary, joins the Yangtze. The middle reach joins with the lower reach of
the Yangtze near Lake Poyang, which is the largest lake in China, in Jiangxi
province. The lower reach flows mostly through Anhui and Jiangsu
provinces. The Yangtze delta plain, which includes the industrial center
Shanghai, is the most developed area in China.
TGP, our main topic in the next few articles, is near the border of
Sichuan and Hubei provinces. The proposed site, Sandouping, is located at
4471 Km from the origin and 1829 Km from the estuary of the Yangtze
River. The gigantic concrete gravity dam of about 1,000 meters long and
175-185 meters high (i.e., the crest level) will make a reservoir of 500-700
kilometers long. The normal water level is a subject of controversy and is
varied from 150 to 180 meters. At the middle of the river there are 23
spillways on the structure, each 7 x 9 square meters in size. Behind the dam,
underneath these spillways are two power generating houses, one of which
contains 12, and the other 14, turbine generators. Each turbine engine is
about 9.5 meters in diameter and has the capacity of 500-720 magawatts.
The two-way navigation devices will be built on the left side of the dam.
Each device will contain 4 to 5 ship locks which operate in series to lift the
passing ships and barges for more than 100 meters in vertical distance.
The proponents of TGP have emphasized three major benefits of the
project: (1) flood control on the Yangtze River, (2) generation of a large
amount of clean energy, and (3) improvement of navigation on the Yangtze
River. The higher the dam is, they claim, the more benefits it will create. On
the contrary, the opponents of TGP have pointed out that a higher dam will
create much more negative effects and will devastate the ecology and the
environment of the Yangtze on a much larger scale. It is the purpose of the
following articles to examine the goals and the effects of TGP in detail. The
two different plans, namely, the 150-meter scheme and the 180-meter scheme
(with the normal water level of 150 and 180 meters, respectively), will be
discussed separately.
Table II. Major parameters of TGP [2].
Parameters 150-meter scheme 180-meter scheme
Crest height (m) 175 185
Total storage vol. (m^3) 19.7 billion 44.6 billion
Active storage (m^3) 9.4 billion 18.4 billion
Flood control vol. (m^3) 7.3 billion 24.9 billion
Power capacity (MW) 13,000 18,720
Annual output (KW hr) 67.7 billion 89.1 billion
Notes:
[1] Excellent regional maps of China can be found in The Contemporary
Atlas of China (1988), edited by Nathan Sivin et al., Houghton Mifflin
Company, Boston.
[2] Data in this and the following articles, unless quoted, were taken from
Tian Fang et al, 1988. The abbreviations of the units are as follows.
M: meter, Km: kilometer, M^2: square meter, M^3: cubic meter, KW: kilowatt,
KW hr: kilowatt hour (i.e. a "du" in Chinese), and MW: megawatt.
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