Sanmenxia Dam, China
Once this massive dam was designed to become a lasting monument to Chinese-Soviet friendship. Today, more than 20 years after the Chinese-Soviet quarrel became public, the dam remains an unfinished lesson in the complexities of taming the turbulent, wayward Yellow River, once known as "China's sorrow."
Since historical records began to be kept, there have been more than 1,500 floods along this river. So, when in 1952 Mao Tsee than 1,500 floods along this river. So, when in 1952 Mao Tse-tung inspected it and issued his call, "Work on the Yellow River must be well done," it was natural to think in terms of building a dam at Sanmenxia (Three Gate Gorge). The aim was to regulate the river's flow, to promote irrigation, and to generate electricity.
This was the period of Chinese-Soviet brotherhood. Soviet advisers designed the dam, after the manner of the huge dams they had built in their own country. They thought big: Sanmenxia was to impound 35.4 billion cubic meters (46 billion cubic yards) of water and generate 1.2 million kilowatts of electricity.
"We knew there was a silt problem," dam engineer Song Lianzeng recently told the Monitor. "But the Russians assured us that they had designed the dam in such a way that it would be good for a least 50 years. We believed them."
It did not turn out of the way soviet advisers predicted. But that is not surprising, considering the river's fearsome past -- both in the myths of ancient China and in the reality of historic flooding.
Today, despite its limitations, Sanmenxia is one of 46 projects large and small along the whole length of the Huang Ho -- the Yellow River. They are designed to control the river, increase irrigation, and generate electric power. The problems of a many-tentacled river system like the Yellow River's can only be tackled and solved in an overall way, according to Chinese engineers. This may be the most valuable lesson learned from the building of Sanmenxia dam.
At Sanmenxia, the Yellow River used to split into three short channels boiling with rapids named Devil's Gate, God's Gate, and Man's Gate. Legend says that Yu the Great, one of China's semimythical early rulers, hewed out of the channels with an ax. Perpendicular gray and yellow cliffs girt with red-streaked rock hem in the river at Sanmenxia, making it an ideal place for a dam.
Three channels have disappeared forever, buried under 200,000 cubic meters ( 260,000 cubic yards) of concrete. Today there is nothing to hint of the backbreaking toil it took to tow small riverboats up a narrow canal that avoided the rapids by hugging the cliffs of the northern bank. Behind the 106 -meter-high dam (350 feet), a placid, serpentine sea stretches toward the western horizon.
Below the dam, the river winds its way to the plain and the sea -- wide, shallow, somehow looking tamed by the towering dam with its 12 sluice gates and two silt-diversion tunnels through which it has just come.
Basically, according to engineer Song, the Yellow River has been brought under control. He emphasized the word "basically" to show that some difficulties remain.
Chinese scientists and engineers have recognized, understood, and made use of the Yellow River -- and reformed it -- the voluable Mr. Song said in interview in the living room of what used to be a Soviet adviser's residence.
"But this is a very complicated river, and we have by no means solved all its problems."
Mr. Song, whose formal title is director of construction in the first project bureau (i.e., Sanmenxia) of the Ministry of Water Conservancy, had just finished a hard day's work at the dam. He has been with the Sanmenxia project since the beginning, along with his colleague Chen Rongyu, planning commissioner of Sanmenxia City.
Silt is the Yellow River's primary and most persistent problme, Mr. Song said. The silt-diversion tunnels carved through solid rock and visible today at the dam had not been in the original plan, he continued. The whole experience of building the dam had been a process of trial and error. He said he and his fellow engineers had had to find out, under successive adverse circumstances such as the Chinese-Soviet quarrel and the Cultural Revolution (1966-76), how to tame the unruly river.
The Yellow River starts as a clear sparkling stream in the high mountains of Qinghai, adjoining Tibet. It remains generally clear for more than a thousand miles as it meanders from east to west, then turns north in a great loop up into the deserts of Inner Mongolia. Then, turning south, it passes the loess highlands of northern Shanxi. Here the silting begins, as the loess crumbles and falls into deep gullies after each rare, torrential rain, thence to beswept down into the Yellow River and its tributaries.
Every year the Yellow River carries 1.6 to 1.7 billion cubic meters (2 to 2.2 billion cubic yards) of silt on its shallow, swift passage to the sea. After the cliffs of Sanmenxia, it comes down onto the flat wheatlands and cotton fields of the North China Plain. Three-fourths of the silt goes down to the sea , forming a rapidly growing delta at the river's mouth. One-fourth remains on the river bottom, raising it until at Kaifeng, once the imperial capital of the Sung dynasty, a person might think he saw boats sailing in the sky, so much higher that his own street level is the river.
Only the continuous building of dikes ha managed to contain the Yellow River once it reaches the North China Plain. Even then, if summer rains are heavier than usual, or if the dikes have not been well built, the river bursts its bounds, causing widespreed death and destruction. In winter, a pileup of ice floes can also breach dikes.
During the early days of dam construction the Russians lived in a comfortable compound in Sanmenxia City, 24 miles from the dam site. In their dining room they were assigned two veteran cooks who could prepare Western-style dishes, plus all the fabulous repertory of Chinese cuisine.
"As individuals, our relations were quite friendly," recalls Sun Jian, manager of the compound, which today is called the Friendship Guest House.
Work at the dam site began in 1957, and with 25,000 blue-tunicked laborers toiling from dawn to dusk, by the 1960 the dam was basically complete.
Then, when just one 145,000-kw. generator had been installed and other heavy equipment, including a 350-ton crane, was yet to come, Soviet advisers abruptly pulled out of Sanmenxia, as they did from all other projects they had been aiding in China. They took all their charts and drawings and tore up contracts for the supply of promised equipment. The Chinese-Soviet quarrel, which had been going on behind closed doors, burst onto the front pages of newspapers around the world. "It was our moment," Mr. Song recalls.
"We were still just beginning our industrialization, and the heaviest crane we could make then was only 100 tons. Premier Chou En-lai himself gave the order to the Taiyuan machinery plant to give highest priority to designing and building a 350-ton crane. And the plant came through -- magnificently."
Generators were more complicated, entangled in the silt problem. "In 1961 we began impounding water," Mr. Song said. "But 1962, as the water level rose higher, we realized that silt was clogging up the river behind the dam all the way to tributaries like the Wei and the Fen, dangerously raising their level and endangering the ancient capital, Xian [Sian].
"Something had to be done, and done quickly.Again, it was Premier Chou who made the correct but very courageous decision in 1963 to release all the water we had impounded in the dam. In other words, it was as if we had never built the dam. We had to start all over again.
"We groped about until the mid-1960s, trying to find a way out. Then we got the idea of digging those silt-diversion tunnels you saw, through the cliff on the northern bank. We also decided to open eight holes below the 12 sluice gates. These speeded the rate of discharge from the original design of 3,000 cubic meters per second [3,900 cubic yards] to 6,000 cubic meters per second.
"We also had to lower the generators and reduce their size. Instead of the 50-meter drop the Russians had designed, we had to work out a 30-meter drop, so that electricity could be generated even when the water level was low."
The Cultural Revolution further delayed progress. Fifty-thousand-kw. generators, built in China, were installed slowly. The fifth and last generator was put in only in 1979. Last year was the first year that the dam generated electricity at its rated capacity, 250,000 kw., according to figures here. This is a far cry from the 1.2 million kw. originally projected.
Today, according to Mr. Song, Sanmenxia basically is not a storage dam but a dam to regulate the flow of Yellow River water. The reservoir stores a modest 1 .6 billion cubic meters, not the 35.4 billion projected by the Russians. At the height of the rainy season, in July and August, all 12 sluice gates and both silt diversion tunnels are wide open, letting both the water and the silt flow out as if the dam never had been.
Ideally, the force of the discharge should be sufficient to sweep the silt all the way out to sea. But the problem of silt accumulation still remains in the lower reaches of the river.
As for ice floes, however, Sanmenxia dam has been quite effective, Mr. Song says. The dam releases water just before ice begins to form on the lower river, thus keeping it from becoming thick enough to press against the dikes. There have been no ice disasters since the dam was built -- and no floods. "Now that you know all you know about the river, and the silt problem, do you still think it was worth building the dam?" Mr. Song was asked. "Oh, yes," came back the reply, instantly. "We have achieved all our original goals except one. First, flood control, as I just explained to you. Second, irrigation.The dam has made possible the irrigation of 40 million mu [6.6 million acres] of hitherto dry land. Third, electric power." On this point, another engineer at the site said that there were plans to double the current 250,000-kw. Output by putting in three more larger generators.
"The only goal we have not achieved is navigation. The Russians said the dam would make possible the use of the river below the dam by 500-ton boats. That goal has had to be abandoned because we simply are not storing enough water." The dam was budgeted to cost 600 million yuan ($400 million). It actually cost 700 million yuan, and subsequent work has brought the total spent on the dam so far to over 1 million yuan ($666 million), Mr. Song said.
What of the future? Although silt in the reservoir has ceased to be a major problem, on the lower reaches of the river silt accumulation continues to be serious."People just have to continue raising the dikes higher and higher," Mr. Song said.
In his opinion, a permanent solution can be found only by tackling the silt problem at its source -- stopping the erosion of the loess highlands by planting trees. This is necessarily a long-term project, but Mr. Song sees no alternative. In addition, dams and other measures to control the river before it gets to Sanmenxia wiil help to reduce the dimensions of the problem.