(May 31, 1994)
NEVER DAM THE THREE GORGES
An Interview with Professor Huang Wanli1
by Dai Qing
Dai Qing: We know you were the only person who contended in 1957 that damming the Sanmenxia Gorge on the Yellow River should not be allowed. Now, you hold the same view on the Three Gorges project. May I ask, then, whether you oppose damming any river?
Huang Wanli: No. As a hydraulic engineer, I’ve never opposed the idea that a flood-control project should, wherever possible, combine such functions as irrigation, navigation, and power generation. However, in designing a major project, we cannot be concerned solely with engineering calculations. We must have insight into the many fields of science and the humanities, and have sufficient understanding not only of engineering, but also of hydrology and geomorphology. As far as the Yellow and Yangtze rivers are concerned, I maintain that damming the deposition reach of a main river course, such as at the Sanmenxia Gorge project, should not be allowed. The Three Gorges project, however, is located in the scouring reach of the Sichuan Basin. It could be constructed if the bed-forming material of the reach were not so coarse. Such coarse material will not pass through the dam and will block Chongqing harbor after the dam is constructed.
Dai Qing: What do you mean by the “deposition reach”? Isn’t it the case that the Yellow River’s sediment builds up mainly in the alluvial plain2 at its lower reaches? Why do you call Sanmenxia Gorge a “deposition reach”?
Huang Wanli: Sanmenxia Gorge’s situation is rather complicated. From the town of Mengjin upstream, the Yellow River does have a deposition reach. But only at Sanmen (Three Gates) has the base rock of the river bed been lifted up due to igneous intrusion. This is a deposition reach inserted into the middle of the scouring reach of the Yellow River-a very irregular topographic formation. In 1957, it had yet to be studied; water engineers couldn’t appreciate its peculiarity. It was said that once water conservation was improved in the upstream areas, there would no longer be sediment flushed down from the Yellow River. In the feasibility study for the Sanmenxia Gorge dam project, I was alone in insisting that the dam should not even be considered. Furthermore, only one engineer argued for a smaller dam. To reconcile with the majority opinion, I suggested that, if the dam must be built, then the sluice gate at its base should be left open in order to flush out sediment. For when we were dealing with the Yellow River, at least we knew it was a river with extremely high sediment content. Everyone agreed with my idea, except the Soviet experts, who insisted that it be blocked. As a result, the upstream course was silted up in barely two years, and the project had to be reconstructed.
Dai Qing: Is the silting pattern of the Yangtze in any way different from that of the Yellow River? Do you believe that no dam should be built on the deposition reach of a river?
Huang Wanli: In the Yangtze Valley, from Chongqing upstream, there exists the Sichuan Basin, which experiences high rainfall. There, ground vegetation cannot totally absorb the abundant volume of water, so the surplus rainfall flushes down to the lower positions, creating thousands of creeks and streams which are eventually gathered in the Yangtze’s upstream tributaries. For the last 100,000 years this water has been reshaping the surface of the earth and deepening the river course, creating the gorgeous scenery along the Yangtze Valley from Sichuan downstream to Yichang. The topographic formation determines that the debris of igneous rock and sand created by weathering is carried by the river all the way through Chongqing and Yichang to the mouth of the Yangtze, where it is deposited on the slope of China’s eastern continental shelf. The debris deposited on the continental shelf by this process is several kilometers deep. This continuous process has left us with the Yangtze’s alluvial plains, which support the livelihoods of 500 million Chinese people.
The scouring and deposition process is the reason why the Sichuan Basin-which is on the scouring reach-has never silted up. The Yangtze and its tributaries upstream of Chongqing scour large amounts of gravel mixed with coarse sand which is flushed down river when floods occur. All of this sediment-from the Yangtze and its upstream tributaries-must pass through the Three Gorges. Once the Three Gorges is dammed, the river’s flow will slow and the sediment will deposit in the backwater reach where it will block Chongqing harbor.
While a dam should not be built on a deposition reach, one may be constructed on the scouring reach. The Gongzui Reservoir on the Dadu River is a successful example. The Dadu Valley is small but the flow of the river is strong. In the 16 years since its completion, the dead storage of the reservoir has completely silted up. Although it can no longer perform its flood-control function, we do not have to remove it by blowing it up; its power plant still works. So what I mean is that, as long as a dam does not obstruct navigation upstream, nor claim arable land, it may be constructed on a scouring reach. Once it becomes silted up, let it be.
There is a German practice however, that as a small dam is built, a sluice gate is left underneath, so that the sediment can be removed at a later date.3 Most dams built in this manner remain in good condition, and can be used for power generation, flood regulation, and irrigation. The focal point of the present controversy over the Three Gorges project is whether or not the Yangtze has a significant amount of coarse sand and gravel (i.e., bedload) and whether such material moves downstream. The Yangtze Valley Planning Office (YVPO) considers the movable bedload immovable, remaining constant at one spot. A simulation test under this assumption is meaningless. According to basic hydrogeologic theory, all of the rocks in this area may move downstream. This of course constitutes a huge amount of sediment, and it is from here that I start my argument. Do not forget that I have witnessed this movement. When I headed a survey team in the 1940s I saw rocks rolling in the flow with my own eyes.
Dai Qing: Is it possible to measure the movement of the rocks and gravel that the water carries down? What factors determine this movement?
Huang Wanli: It is measurable upstream. For instance, the Gongzui Reservoir was silted up in 16 years. Therefore, it is possible to measure the river’s annual sediment load from this point upstream . From the Dujiangyan dam, it is reported that the river’s annual sediment load is about 2 million m3. If we add the sediment of each tributary, we will get the aggregate amount that goes through the Three Gorges. In principle, it is hard to investigate this factor in a deposition reach, because there the river may drop some of the load it carries before it moves it along again. But it is feasible to measure the amount of rock from the Yangtze that the river carries past Yichang each year, by synthesizing data derived from the small valleys upstream, in proportion to the total area to be investigated. My own estimation of that amount is in the neighborhood of 100 million tonnes.
Dai Qing: Do you mean to say that, in the past few decades, a geomorphic perspective has never been derived from the research of so many engineers?
Huang Wanli: This is a lesson that rivers and mountains continue to teach human beings even though we think we are knowledgeable in the area. Eighty years ago, an American engineer said that a dam builder must be well versed in two areas. One was hydro-engineering, which meant you had to understand how to construct a dam. The other was natural geography and geomorphololgy-in order to tell what impact the dam construction, once complete, would have on nature. This was his advice to the U.S. government. It is also why, in the Tennessee Valley Authority, chief responsibility was shifted from J. L. Savage, an engineer, who knew only how to build dams, to Arthur E. Morgan, a specialist in comprehensive river planning from Ohio. Morgan invited S. M. Woodward, a professor from the University of Iowa, to join him. At that time, geomorphology researchers were dissatisfied with engineers, saying they often made mistakes, whereas the engineers involved in the concrete work were dissatisfied with scientists, saying that they couldn’t solve problems. Few people were well versed in both methodologies.
When I arrived in the United States in 1934, I had already had two years’ experience as a railway and structural engineer; then at Cornell University, the University of Iowa, and the Engineering Institute of Illinois, I branched out to astronomy, meteorology and topography. This has enabled me to really know whether a dam should be built, and where it can be built. A water engineer does not have to be a geomorphologist, but with a basic understanding of the field, he can gain a deeper insight and a broader view. In other words, any engineering project must involve both comprehensive and technical understanding; you must have the former before you can start the latter.
Dai Qing: But many distinguished scientists were also involved in the leading group’s assessment of the Three Gorges project. Why, in your opinion, did their theoretical expertise have little influence on the project’s key technological issues?
Huang Wanli: I don’t mean scientists should be used to design a dam’s operational processes. What I recommend is that engineers be informed of the findings of scientific research. To ask a geomorphologist to choose a location for a water engineering project is to ask him to do something for which he is not trained. On the other hand, to ask a water engineer to learn some geomorphology is a much more reasonable request. Scientists have their domains, their theoretical approaches, and are preoccupied with the most fundamental issues. In the field of application, it is up to the engineers to grasp the theories that scientists have provided and develop their own operational processes. One of the remarks that led me to be labeled as a “rightist” in 1957 was made exactly on this relationship. Mao Zedong proposed to relate theory to reality in the 1940s, saying that doctrines were useless and that only the kind of Marxism-Leninism that was produced in the rural hinterland4 could solve China’s real problems. In the 1950s, following this “great teaching,” a batch of people started to use “reality” as an excuse for theoretical ignorance. I said: “There is no theory that cannot be related to reality, only realities that one fails to explain in theory.” Now, 35 years have passed, and we still have different views and estimations of the Yangtze’s sediment.
Dai Qing: Why has it been decided to build the dam at Sandouping, where the river is about two kilometers wide, when there are so many narrow gorges in the Yangtze? Wasn’t the building of a two-kilometer-long dam decided, I’m afraid, just for the project to look magnificent?
Huang Wanli: For all water engineers, the narrower a dam is, the more cost-efficient it is from an economic point of view. Otherwise, why build a dam in a valley? But the Three Gorges is a complete reversal of the ideal: The dam designed for Sandouping only has a reservoir width between 500 meters and one kilometer. But it expands to two kilometers at its crest length, creating a winding reservoir 600 kilometers long. This is unprecedented. The rationale for this design, which the YVPO does not seem to want to address openly, is that there is actually no other alternative. For in the entire reach of the Three Gorges, only at Sandouping is the river bed made of igneous rock. But they seem to have forgotten that there is still about 35 meters of gravel on top of the base rock. During construction, this deposit is to be totally excavated, and 35 meters is to be added to the height of the dam, which will contribute nothing to the reservoir’s storage capacity-uneconomic indeed. In addition, the resettlement of more than one million people, which will cost one-third of the entire budget, is unheard of. In my calculation, the combination of these factors will produce total costs seven times more than that for a power plant of the same capacity! The design is absurd, and overpriced. By contrast, just look at the Wujiang River hydro power station. On the narrow watercourse, there is just an arch dam to let the flood spill over it, with the power plant fixed within, combining its three functions perfectly. And at the Guanting Reservoir in Beijing, the body of its earth dam extends only 100 meters. Of course, half of the space above the dam is silted up, and so a large part of its flood-control capacity has been lost. But it has been there for 40 years.
Dai Qing: If, according to the present plan, a 175-meter-high dam is built at the Three Gorges, how long will it take before things begin to go wrong upstream?
Huang Wanli: In terms of sedimentation, the Yangtze is different from the Yellow River. The silt head of the Yellow River has passed Chang’an and reached Xi’an. It will stop only when it meets with an upstream slope. The Yangtze’s alluvial reach is originally steep enough to eliminate sedimentation. But if the flow of the river slows down, and drops the gravel at Chongqing, that would be equivalent to erecting a new dam, making it possible for the sediment to build up. This is unavoidable unless the river bed is somehow lowered. But who can do that? There is no chance for the sediment build-up to travel very far; it will stop where the slope becomes abrupt. But this is enough to raise the flood levels at Jiangjin and Hechuan (Sichuan), and cause frequent flooding. The affected area will not exceed one-fifth of Sichuan. But, think of it, one-fifth of Sichuan subject to floods-what a catastrophe!
The most serious problem is that once water storage begins, Chongqing harbor will silt up in less than 10 years. Under these conditions, in order to ensure upstream navigation, the dam will have to be blasted off. But the dam is deep in the valley. Where can the debris be put when there is no level ground? This would be extremely costly. To the east of Sichuan will be the reservoir’s submergence zone, to its west will lie the destruction of Hechuan and Jiangjin, and with the obstruction of navigation will come problems with external communication. The residents of Sichuan will naturally begin to ask why, for no reason at all, they must make such sacrifices: I would not be surprised. You must know of the “Road Protection” movement5 toward the end of the Qing Dynasty. It was when local interests were compromised in 1911 that an opportunity for the Republican Revolution to topple the imperial regime occurred.
Dai Qing: But how can the Three Gorges project, now already under way, be stopped? So many years have been spent on its assessment, and so much has been done for its preparation. If it is stopped at this point, does it mean that all the previous efforts are totally wasted?
Huang Wanli: My view is different from many others. They are concerned with whether, according to the state’s economic capabilities, the project should be started somewhat earlier or somewhat later. But I insist that never should the deposition reach of a river be dammed. The scouring reach may be dammed, provided it’s not navigable, and the project does not claim arable land. The Three Gorges project is on a scouring reach; it is on a golden waterway, as it is commonly called. This project would also involve the submergence of 500,000 mu of farmland and the resettlement of more than 1 million people-it should not be taken lightly. Unfortunately, even if I tried to explain this point to my students, they might not accept it. The people who have devoted so much work to the project and have spent so much money will try anything to defend their project. Until 1986, when its publicity campaign began, I never really thought that someone would try to build a dam at the Three Gorges. So, I declared my point of view in the newspaper, Science and Technology Tribune. I hoped that there would be a public debate so I could elaborate on my concerns. Damming the Three Gorges might well have been Dr. Sun Yat-sen’s grand view of the future, and it might well have fit Mao Zedong’s poetic fantasy, but we engineers must treat the issue with a sense of responsibility. I have never been given a chance to speak out.
The construction of the Three Gorges dam (to follow the present preparatory works for the project) has not yet begun. What has been done so far is of no major consequence. It does not do serious harm to the river valley to relocate some local residents, to plant some trees on higher ground, and to build some bridges. This work would not be a total waste even if the dam project was canceled. However, the sooner it is canceled, the better.
Sources and Further Commentary
1Huang Wanli has been a professor in the Hydraulic Engineering Department of Qinghua University, Beijing, since 1953. He obtained his doctorate in engineering from the Engineering Institute of Illinois. He returned to China in 1937, after having worked at the Tennessee Valley Authority, and has held various positions including: chief advisor in water engineering technologies at the State Commission of Economic Affairs, chief of the bureau of water resources of Gansu province, and chief advisor to the Northeast China General Bureau of Water Resources. This interview, conducted in August, 1993, was not part of the original Chinese edition of Yangtze! Yangtze!
2Flood plain created by deposition of sediment from river floods.
3The debris may be flushed through the sluice gate by manipulating the river flow by upstream reservoir operations.
4 Marxism derived directly from the experience of guerrilla warfare not from bookish readings of Marx. Implicit is a lopsided emphasis on practice and contempt for theory.
5A reference to the outbreak of violence in Sichuan as local elites resisted the efforts of the central government to take over the province’s railroads and run them with foreign financial assistance.
Categories: Three Gorges Probe