The Three Gorges Project. Part III: The History of PRC Dams.
"I agree to build this dam. The plan in the current document is one
thing, the unexpected problem encountered during the construction process
is another. We should be prepared to revise our plan at that time."
- Mao, Zedong, in his instruction to approve
the Gezhouba project in 1970.
Before I go into the details of TGP, I'd like to mention a few words
about the two major water projects after the founding of PRC, namely, the
Sanmenxia (Three Gate Gorge) Reservoir and the Gezhouba project. They will
be compared with TGP in the later texts.
After PRC was founded in 1949, China has built more than 80,000
hydroelectric power stations. Among them, about 84 are of large or middle
sizes (i.e., > ~1000 Megawatts). These dams have contributed much to power
up the remote villages, to provide irrigation to the dry farmland, and to
alleviate the flood threat in most countryside. However, during those
"revolutionary" days, many of them were started without proper
preparation. Those dams were often being built at the same time when the
field survey and the designing were going on. Unfortunately, the two major
projects, i.e., the Sanmenxia Reservoir on the Yellow River (Huang He) and
the Gezhouba project on the Yangtze River, are two notable failures among
the water projects in China.
I (and probably many of us) first heard about the failure of the
Sanmenxia Reservoir from the TV series The River Elegy (He Shang). The
Sanmenxia project was completed during the early 60's. It is located at the
lower reach of the Yellow River, near the border of the 3 northern provinces:
Shaanxi, Shanxi ("the west of the mountain") and Henan. It was originally
designed to have the capacity of 1200 Megawatts as well as the flood control
benefits. However, The design of the Sanmenxia project had apparently
underestimated the rate of siltation to the dam. The Yellow River, by carrying
1.6 billion (metric) tons of silt to the sea each year, is the most silt-
laden among all the rivers in the world. As a result, only in 2 years after the
project was finished, nearly half volume of the reservoir was silted up. The
siltation were expanded rapidly beyond the tail of the reservoir (i.e., the far
end from the dam site). The elevated water level would soon threaten the
ancient capital city, Xi-an. At the mean time, the enlarged soil salinization
presented a severe problem to the north China plain.
In order to prevent the disasters, the Sanmenxia Reservoir was rebuilt
for several times. It has to give up storing water during flood season (i.e.,
the summer and the fall) of the a year when the siltation is the most serious.
It can no longer participate in flood control. The capacity of the dam is
reduced to 250 megawatts, only 20% of what was originally planned.
Moreover, it has to stop generating power during flood season when the
water flow is abundant, because the huge amount of silt (yes, silt again!) will
damage the turbine engines. During the water storage period (i.e., after the
flood season), the downstream river bank is flushed by clean water (because
silt is now trapped behind the dam) and lost more than 50% of the soil. Four
irrigation projects downstream were damaged or removed due to the
rebuilding of the Sanmenxia Reservoir, not to mention the huge amount of
manpower and capital wasted in the project. Such a disastrous project was
opposed by some experts before it was started. Even the Soviet experts at
the time admitted frankly that they lacked the experience to deal with the
silt of the Yellow River and expected, from the data provided by their
Chinese counterparts, the lifetime of the reservoir to be at most 50 years.
These opinions, of course, were all ignored at the time.
The Sanmenxia Reservoir is hardly mentioned in public. In contrast,
the recently accomplished Gezhouba project has been widely hailed by the
news media in China. As mentioned in Introduction, Gezhouba is located
near the intersection of the upper and middle reaches of the Yangtze River.
It was proposed by "Chang Ban" during the Cultural Revolution and got
approved by Mao in 1970 (see his approval at the beginning). It was
supposed to generate electricity in 3.5 years and be completed in 5 years.
The cost was originally estimated to be 1.35 billion yuan (not including
interest). It was said that the Gezhouba project was started hastily, before
the preparative work was completed, in order to catch Mao's birthday. What
happened later was exactly "predicted" by Chairman Mao. The project came
to halt two years later because the siltation problem affected the navigation
on the Yangtze River. It took 2 years to perform the modeling experiment
for siltation and to revise the design. The project was restarted in 1974,
with the revised cost estimate of 3.43 billion yuan. It finally took 19 years
and nearly 5 billion yuan (not including interest) to complete the project.
The Gezhouba is only 47 meters high, with the capacity of 2715
megawatts. The investment per megawatts is 180 yuan, or, 300 yuan if the
interest accumulated during the 19 year's construction of the project is
included. That is more expensive compared to the other dams in China (the
average is about 150 yuan/megawatt). The volume of the Gezhouba is only
2.3 billion cubic meters, too small to regulate the water flow downstream
(not to mention flood control). In practice, it can only generate about 1500
megawatts even during flood season and 700-800 megawatts during dry
season. Due to the budget limitation, its prolonged construction period has
delayed the other projects which will have similar capacities but take much
less time. The construction process also affected navigation and caused the
upper reach area (e.g., Chongqing) a loss of nearly 30 million yuan. The
Gezhouba project has improve the navigation of the Three Gorges area to
some extent. However, the accidents of the ship lock happened so frequently
that, among 655 days from 1981 to 1983, the navigation on the Yangtze
River had been interrupted for as many as 174 days.
Although the Gezhouba is acclaimed to be a technically successful
project (after the revision), the opponents pointed out that it is built at a
wrong place in terms of general strategy. Usually smaller dams are built
upstream of a larger dam to regulate the flow and to reduce siltation to the
larger dam. The relationship of Gezhouba and TGP is just the opposite: the
Gezhouba is 40 kilometers downstream of the proposed TGP, a dam at least 3
time larger in scale. But that doesn't seem to matter. It was said that the
Gezhouba is merely a preparative project for TGP, or, a project to prove the
feasibility of TGP. According to "Chang Ban", TGP must be "mounted on
horse" (Shang Ma), and the sooner, the better. The only question is: can TGP
be really completed in 19 years as proposed, the same amount of time as the
much smaller Gezhouba?
- Chianfan Zhang;