The Three Gorges Project. Part VI: Navigation.
The Yangtze River, China's "golden waterway", plays an important role
in the economy of the upper reach area. In that mountainous area,
navigation is almost the only way of long-distance transportation. For
Chongqing, a major port city in Sichuan province, 90% of material is
transported by water. Although the Yangtze River and its tributaries possess
more than 70,000 kilometers of waterway, the navigation condition of the
"golden waterway" is rather poor. Barges larger than 1,000 tons can only
travel within a limited path of 2,500 kilometers, mostly in the middle and
the lower reaches of the Yangtze. A large part of the upper reach and most
tributaries only allow transportation of barges below 100 tons (see Table I
for more detail). In 1985, about 5 million tons of material had been
transported on the Chuan Jiang. That number was expected to reach 10
million tons in 1990 (current status unknown) and 25 million tons by the
end of the century. Obviously, whether TGP will improve or deteriorate the
navigation condition of the Yangtze River will largely affect China's economy.
Table I. Navigation condition of the Yangtze River in 1985. From Tian Fang,
et al., 1988.
Stretches: Length (Km) Capacity for barges (tons)
Shanghai - Wuhan 1125 5000
Wuhan - Chenglingji 250 3000
Chenglingji - Yichang 470 ~ 1000
(^^ = the Jing Jiang)
Yichang - Chongqing 660 < 1500
Chongqing - Yibin 385 < 300
(Yichang-Yibin = the Chuan Jiang)
Yibin - Xiludu 183 ~ 100
The Jinsha Jiang only small boats
Note: In 1985, the Yangtze and its tributaries had transported totally 300
million tons of material, among which the mainstream carried 120 million
tons. TGP will only affect the condition of part of the Chuan Jiang, i.e.,
the waterway from Yichang to Chongqing.
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Because TGP will create a man-made lake upstream of Yichang, it will
dramatically increase the depth of water up to 400 kilometers from the dam
and, thus, improve the navigation condition of the lower reach of the Chuan
Jiang. According to "Chang Ban", the 180-meter scheme will improve
navigation up to Chongqing, a port city at more than 600 kilometers
upstream of the dam. Besides, the huge reservoir will make the effects of
local landslides negligible to navigation in this area. In 1981, for example,
due to the presence of the Gezhouba reservoir, the navigation on the upper
and middle reaches was much less affected by the large-scale landslide at
Xingtan, an active landslide area only 27 kilometers upstream of Sandouping.
Nevertheless, the opponents of TGP warned that siltation near the
tail of the reservoir would seriously affect navigation of the upper reach of
the Yangtze River during dry season. Silt tends to accumulate near the tail of
a reservoir due to the movement of backwater. This is a serious problem for a
large dam if a long reservoir is created and the sediment near the tail is hard
to wash away. The accumulated siltation near the tail will elevate the river bed
in this area and create obstacles for navigation during dry season (when the
water level is low). The 150-meter scheme will only improve the waterway
during flood season up to Fuling, which is a city at 483 kilometers upstream
of the dam. However, the 150-meter scheme will aggravate siltation near
Fuling and seriously affect this part of the Chuan Jiang. It was claimed that
navigation to Chongqing would be blocked during dry season.
With the similar arguments, the opponents of TGP claimed that the
180-meter scheme would silt up Chongqing, where a large tributary, the
Jialing Jiang, joins the Yangtze River. They pointed out that the method
proposed by "Chang Ban", "Xu4 Qing1 Pai2 Hun2" ("drain off the muddy and
store the clear", basically the Sanmenxia approach), would not work at all for
TGP whose tail is much farther from the dam. Such method was also applied
to the Liujiaxia Reservoir, a medium size dam at the upstream of the Yellow
River. It was found that this approach could only deal with siltation within 2
kilometers from the dam, a negligible distance for TGP. Moreover, such a
solution,if works at all, runs counter to the flood control function of the dam.
During flood season when the river is rich in silt, TGP has to store water and
trap silt to relief the flooding of the middle reach. This can only seriously
aggravate siltation near the tail of the reservoir and block navigation when
dry season comes.
Therefore, the opponents of TGP believed that 180-meter scheme
could silt up Chongqing and the entrance to the Jialing Jiang. If it happens,
TGP will seriously affect the economy of the upper reach of the Yangtze
River. On the other hand, they claimed, it would only take less than 1 billion
yuan to improve the current waterway of the Chuan Jiang and make it
capable of transporting 25 million tons a year.
We have seen that siltation of TGP is a serious problem not only to the
lifetime of the project, but also to the navigation on the Yangtze River. On
the other hand, other large dams in the world have not found such
complexity so far. For example, the Hoover Dam of U.S. on the Colorado
River, the Aswan Dam of Egypt on the Nile, and the Bhakra Dam of India on
the Sutleij River were all built at the sections of the rivers where navigation
is negligible. And so is the section of the Yellow River where the Sanmenxia
Reservoir is built. In fact, large dams have never been built on important
navigation rivers (e.g., the Mississippi River) in the world. Rivers of less
navigation importance such as the Tennessee River, the Columbia River, the
Danube, and the Rhine, are all much less silt-laden compared to the Yangtze
River. For example, the Paranaiba River of Brazil, where the Itumbiara Dam
(one of the largest dams in the world) is built, carries only 1/7 of silt
compared to the Yangtze. Besides, reservoirs of total volume of 130
billion cubic meters have been built upstream of the Itumbiara to trap most
silt. In contrast, there are no large reservoirs in the upper reach of the
Yangtze River to effectively reduce the siltation of TGP.
The opponents of TGP also worried about a technical aspect of the pro-
ject, namely, the reliability of the navigation device containing multiple ship
locks. To lift 10,000 tons of weight over a distance of more than 100 meters,
the design of the vertical ship lift, which contains a series of 5 ship locks,
will surely break the world record (see Table II). Of course, there
should not be any difficulty in theory. However, the navigation of the
Yangtze River may be interrupted if any one of the five locks has a problem.
We have already seen that the problems with the ship lift of the Gezhouba,
which only has one ship lock and is technically much simpler than that of
TGP, had already interrupted navigation and caused economic loss to Sichuan
province. Needless to say, TGP will have much greater probability for the
failure of its navigation system.
Table II. Several technical parameters of TGP. From Dai Qing (ed), 1989.
Items TGP Domestic record World record
Multiple locks 5 2 4
Chamber size (M^2) 34 x 280 8 x 56 18 x 100
lock weight (tons) 11,500 450 8800
Height of lift (M) 113 50 73
For each turbine engine:
Power capacity (MW) 680 320 700
Turbine diameter (M) 9.5 6 9.2
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Professor Zhou, Peiyuan, former director of the Chinese Academy of
Science and a member of "Zheng Xie", told his experience when he visited the
Gezhouba. There he asked an official of the Gezhouba project how long it
would take to pass the dam. The answer was "45 minutes". He then asked the
same question to the captain when he boarded the ship. To his surprise, the
answer he got this time was "usually 4 or 5 hours". What made the difference?
Well, the ship carrying "the big shot", such as members of "Zheng Xie", would
surely get lifted as soon as they get there. But normally the ship lift will
wait until "small potatoes" fill up the chamber, and that usually takes several
hours. Naturally, the next question is: how long will it "usually" take
to pass TGP, a much higher dam claimed to provide much greater navigation
benefit?
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