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How China Dammed the Yellow River
The Sanmenxia Dam
You can watch the YouTube video for this one at this link below:
Author’s note: I had first come across the Sanmenxia Dam when I was doing the video on the Three Gorges Dam. The Three Gorges covers just barely half of the Yangtze’s watershed, but the Sanmenxia on the other hand covers over 90% of the Yellow River’s - making it a much more effective dam in terms of floods.
As someone who has to manage multiple, conflicting interests on a daily basis - I am fascinated with the political decisions and engineering tradeoffs made in creating this dam. For all of its early shortcomings, the construction of the Sanmenxia Dam really illustrates the Party’s determination to fix its mistakes when something goes wrong.
At the same time, engineers and surveyors are right when they point out that the Yellow River’s silt problem is not an entirely natural event, but is tied to the environmental destruction of upstream land. You can jigger and rejigger the dam all you want, but the best long term solution is to address the Loess Plateau’s soil erosion problems.
I remember that China has done a lot of work to try to address the sand erosion issues as part of its desertification work. But it is a dilemma that I think is tough to resolve. The areas most vulnerable to desertification and soil erosion in China’s north are poorer areas that live off the land. Acquiring that land and re-foresting it is going to have a negative economic impact.
The Yellow River is China's second biggest river. It is seen as the birthplace of China's civilization and is a source of much of its prosperity.
Yet at the same time, the Yellow River has brought great tragedy to the Chinese people. Thus the nickname: "China's Sorrow". Major floods throughout the years - natural or otherwise - have killed hundreds of thousands.
For its first great achievement, the People’s Republic sought to bring China's sorrow under the control of man. Thus came about the country's first great dam: the Sanmenxia.
The Silt of the Yellow River
The Yellow River is the most silt-heavy river in the world. This mud comes from the Loess Plateau. This area is home to China’s cradle of civilization. Its soil is some of the most erodible in the world. A few days of rain can trigger a dozen mud slides.
For farmers downstream, the silt helps make the North China Plain a fertile farming ground. But the Loess can also bring too much of a good thing. Its soil is so highly erodible that just a little bit of rain would trigger torrential mudslides pouring into the river.
When the rains come and erode away their farms, farmers can no longer produce food. It leads to one of the big consequences of the Yellow River floods. The huge number of deaths come not only from the actual flood, but also the famines that follow.
This silt also gives dam engineers headaches because it shrinks the capacity of any potential reservoir. It will literally fill up the whole thing with mud.
The Japanese had their eyes on damming the Yellow River during the Second Sino-Japanese War, with the Sanmenxia Gorge area being the top candidate. They never tried anything because of their defeat at the end of World War II. Good. Because had they tried, they would have failed because of this serious silting issue - which their documents show that they clearly didn’t see coming.
A few Americans managed to review the area before the Communist victory in 1949. They said that the Sanmenxia area would be ideal for a power generating dam. But the silt and flood issues would make such a dam difficult to maintain without first addressing the soil erosion issues on the Loess Plateau.
In 1942, American soil conservationist Walter Lowdermilk experimented a bit with planting grasses and trees as well as building "soil dams" across the landscape before the American government ended the project for budgetary and war reasons.
Before leaving, the Americans recommended that any Yellow River dam be primarily for flood control - not power generation. To best serve such a purpose, the dam would be set 100 km downstream from Sanmenxia at the Bali Hutong area.
Ten years later, the PRC government did investigate a potential Bali Hutong dam with the goal of more robust flood control. But doing so could leave the millions of people in the Shaanxi province fully exposed to the whims of the Yellow River's floods. The provincial government argued against such a situation.
Damming the Yellow River
One of the first things the newly established People's Republic of China government wanted to do was to help this vastly rural country industrialize and modernize. Part of this industrialization plan involved damming the Yellow River for clean power generation.
In 1954, the newly installed Communist Party of China invited a number of Soviet advisors to review a potential dam for the Yellow River at the Sanmenxia area. It would be the start of a series of industrialization projects performed in the name of Sino-Soviet friendship.
The project faced challenges from the very start. What did the government want the dam to be? Should it be first and foremost for flood control? Or hydroelectric power? You can’t make a dam that does both really well. Different ministries had different priorities.
For several years, the Soviet team taught Chinese how might to build a dam across the Sanmenxia. They offered a design that balanced between flood control, agricultural water storage, and hydropower generation. It seemed promising. Construction would begin in earnest by 1955.
But changing winds in the Sino-Soviet partnership caused Stalin to completely recall the team by 1960. It left the Chinese on their own for the rest of the project.
Zhou Enlai himself expressed concern about damming the Yellow River at the Sanmenxia. A PRC commission set up in the 1950s had performed an experiment to try and figure out how bad the silting issue really was. They created a small reservoir, expecting it to be filled within 10 years. The silt filled the reservoir in just 3.
Zhou would say at a State Council meeting: "It is possible that the Sanmenxia reservoir would be clogged quickly ... despite the fact that the project has been started, I feel uneasy about it."
The dam design given to the Chinese by the Soviet engineers tried to make the most of a difficult situation. And efforts were underway upstream to improve the soil erosion on the Loess Plateau. Even so, it seemed clear that the dam would be silted within 50 years. The Soviets presented this as an acceptable trade off.
Yeah sure at the end of the 50 years you’ll have to abandon the dam or spend a lot of money cleaning it out, but think about how great things will be before that happens!
Huang Wanli, a hydraulic professor at Tsinghua University with family ties to Mao Zedong, criticized the design for something that he felt was obvious: The upstream soil erosion efforts are not working well enough. The 50 year estimate was made assuming the soil erosion efforts would be wildly, irrationally successful. He also added that to try to artificially mess with the Yellow River’s silt situation would cause substantial consequences in the future in ways we won’t know until they happen.
Huang had no hope of stopping the project - Mao himself wanted it after all - but he suggested modifications. He argued against recommendations by the Soviets that the dam reservoir be set at 360 meters. In addition, he wanted there be the possibility of river water flowing through in case the reservoir gets filled with silt - and so pushed for a diversionary river channel built during the dam’s construction to be made permanent.
However, Huang had run afoul of Mao Zedong. Mao had little respect for intellectual types (his physician's memoirs make this clear), and he felt that Huang's technological complaints were in fact complaints against the Party itself. This is of course, unacceptable. Mao had Huang declared a "rightist" and removed.
You see, by now the Party was crowing about the dam's progress and future benefits. Telling everyone and their mother that this dam would help bring about the industrialization of China through the benefits of hydropower. Propaganda pumped up the dam to the people: Telling them that under the leadership of the Party, nothing can stop the Chinese people from achieving their goals.
It’s a lot to live up to. Behind the scenes, the Party was trying to balance different ideas and goals to bring this dam into reality. Because of the dam's high profile and visibility, resolving these required a surprising number of really senior Party members - none of whom were engineers - to get involved.
For example, the crucial 360 meter height of the reservoir (note that this doesn't represent the dam's actual height, as it's built at a 353-meter elevation). Communist Party secretary of the Shaanxi province Zhang Desheng requested to have the height lowered. Not just because they were worried about the repercussions of the silt load (if the reservoir is full of mud then guess where the water goes), but also because raising the water level of the reservoir just ten more meters means some 300,000 more people needed to be moved from their ancestral homes due to flooding. And it puts the water just 40 kilometers from the critical industrial city of Xi'an.
Relocating villages on such a large scale would be difficult. To be honest, the Shaanxi government probably didn't want the dam in the first place but those local officials knew what would happen if they said such a thing.
But lowering the water level from 360 would affect the dam's hydroelectric power generation. And that's no good.
So. Will it be 360 meters? Or 350 like the Shaanxi government wanted? Or 336 as some other technicians recommended? To deal with all these differing requests, Zhou Enlai himself went to Sanmenxia and convened a big meeting with members from the local governments, the government ministries, and the dam commission. Now all together, they hashed things out.
Two senior leaders of the CCP, Peng Dehuai, former general of the People's Liberation Army, and a guy named Xi Zhongxun (who's son you may be familiar with), argued for retaining the 360 meters. It would help put China on a path of industrialization and bring its economy on the same level as that of Great Britain within 15 years. This was a public Party goal and much was staked on achieving it.
Zhou however was a pragmatic and thoughtful guy. Always has been - and I personally admire that. He struck a softer tone, admitting that much about the river has yet to be known, and negotiated a compromise. 360 meters, but to be achieved after 1967. Before 1967, 325 meters.
Zhou's conservative feelings would be affirmed just a few years later when everything started to go wrong.
Revenge of the Silt
By 1960 the dam was largely completed and the reservoir behind it began to fill with river water. Then things started to go very wrong.
From late 1960 to mid-1962, some 1.5 billion tons of Yellow river silt poured into the reservoir, far more than anyone ever estimated. By 1964, a third of the reservoir's capacity was lost - declining from 9.8 billion cubic meters of water to 5.74 billion.
Worse yet, the silt clogged the mouth of the Wei River - a tributary that feeds into the Yellow River. Water then backed up and submerged valuable farmland. The flood then leached into groundwater supplies. Farmers lost both their ability to grow food and their fresh water.
The Sanmenxia dam's water outlets are set rather high at about 325 meters. This is in contrast to the Three Gorges Dam, which has three outlets set at varying heights along the dam wall. Because the Sanmenxia outlets were placed so high up, over 60% of the silt entering the reservoir stayed there.
The government had hyped up the dam's hydropower generation capabilities. But for now this will need to be sacrificed to deal with the silting issues. After consulting with technicians, they in December 1964 authorized adding two new tunnels on the dam's north banks as well as the repurposing of four steel pipes originally meant for generating hydroelectric power to funnel silt water out of the reservoir.
By 1969, the silt had filled half of the reservoir and further reconstruction would be needed. The dam's outlets were lowered from 300 meters to 287 meters. Secondly, the commission took Professor Huang's suggestion of having the diversionary water channel be made permanent. Eight outlets that had been closed during construction were reopened.
These two renovations greatly compromised the dam's hydroelectric capacity, but improved the silting issue. By 1973, the dam began to operate in a normal, cyclical manner. And China learned an immense amount of information that its engineers would further apply to its future dams.
Today, it manages a drainage area representing 92% of the Yellow River's total drainage area, offering fantastic flood protection for the people living there.
The Sanmenxia dam remains very well-regarded in Chinese history. Its construction is a story of the challenges of building and delivering on the promises of extremely complicated, large-scale engineering projects. And it demonstrates the Party's dedication towards industrialization as well as its determination to fix projects after they've gone wrong.
I think a recurring theme that I keep coming to again and again with videos like these, is that multi-sided decisions are hard. And there isn’t always an obvious way forward - even when approached using “science and engineering”. It's like what I mentioned back in the Taiwan pork video. The science can’t be the end all be all because the science doesn’t actually really say anything. It’s not impartial because humans have to interpret it.
Someone on the outside might look at this situation and make big, sweeping claims in the comments section like as if there was a definitive answer all along. Oh, the science is clear that we should optimize the dam for this and that. But the reality you will find (and as the Party found out) is that you gotta make trade offs. You gotta make human interpretations. And you gotta make mistakes.
I don’t fault the Party for making a decision like this. Ironically enough, I think the Party was the right authority to make such a call. Balancing and satisfying multiple people with different wants is politics - and that’s what the Party is all about.