Zhang Guangdou, a 90-year-old water engineer and professor at Beijing’s prestigious Qinghua University, was garlanded earlier this month with China’s most lucrative engineering prize. He won the Guanghua Award, worth one million yuan RMB (US$120,000), in recognition of his leading role in building several of the country’s big dams.

Forty years ago, Mr. Zhang played a key part in the Sanmenxia disaster on the Yellow River, when the reservoir of what was then China’s biggest dam silted up within two years of operation. Years later, he would also help design the controversial Three Gorges dam on the Yangtze River. His support for the large dams promoted by top Chinese leaders ensured a smooth career, capped now by the million-yuan prize.

Another prominent water engineer, Huang Wanli, opposed the construction of both the Sanmenxia and Three Gorges dams, warning in both cases about the dangers of sedimentation. In the 1950s, after speaking out against the Sanmenxia project, he was denounced and sentenced to hard labour. Almost 40 years later, a letter Mr. Huang wrote U.S. president Bill Clinton about the risk of sedimentation in the Three Gorges reservoir is believed to have helped reverse U.S. support for that project. Because of his opposition to these two large dams, Mr. Huang was punished, and sidelined for decades.

Both Mr. Huang and Mr. Zhang chose to return to work in China after earning degrees in the United States in the 1930s. Both went on to gain prominence in the same field and to work in the same department at China’s top technical university. But there the biographical parallels end. Because of their divergent views on big dams, their political and professional lives unfolded quite differently.

Mr. Zhang earned master’s degrees from the University of California (1935) and Harvard University (1936). After returning to China, he became director of the powerful Water Resources and Hydropower Research Institute in Beijing. Among other projects, he was in charge of designing Beijing’s Miyun reservoir and the Gezhouba dam, the first dam to be built on the main channel of the Yangtze River (40 kilometres downstream of the Three Gorges dam site).

For his part, Mr. Huang earned his master’s degree in hydrology at Cornell University and a doctorate in engineering at the University of Illinois. He worked at the Tennessee Valley Authority before returning to China in 1937, and over the next two decades held several high-level positions with provincial and regional water bureaus.

In 1953, he became a professor at Qinghua University and, in the course of his fieldwork, surveyed 3,000 kilometres of China’s rivers on foot. Judith Shapiro, a professor of environmental politics at American University in Washington, D.C., writes in her recent book Mao’s War against Nature that Mr. Huang’s “extensive study of geomorphology and geography gave him insight that was unusual among those trained in civil engineering, particularly into the interrelation between dams, sediment, and water flow.”

In the mid-1950s, Mr. Huang became concerned about the proposal to build a large dam on the Yellow River at Sanmenxia (Three Gate Gorge, not to be confused with the Sanxia or Three Gorges dam on the Yangtze). Mao Zedong had toured the area in 1952 and issued an ambiguous slogan – “Work on the Yellow River must be carried out well” – that the pro-dam lobby used to support its case.

At a meeting called in June 1957 to discuss the project, Mr. Huang was alone among more than 70 experts in arguing that the dam should not be built. A stated goal of the project was to trap sediment behind the dam to create “a clear Yellow River” in the lower reaches. Mr. Huang insisted the idea was folly and contravened the laws of nature. But if the project did go ahead, he argued, silt-discharging tubes and sluice gates had to be built so that sediment carried by the notoriously muddy river could be flushed out of the reservoir.

Although the design for the 340-metre-high Sanmenxia dam that was subsequently approved by the State Council included the outlets and tubes advocated by Mr. Huang, his advice was ignored during the construction phase, with tragic consequences.

In a detailed account of the debacle in The River Dragon Has Come!, writer Shang Wei says “the dam supporters and Soviet experts had made a serious mistake. … [U]nder the leadership of Professor Zhang Guangdou, and based on suggestions from the Soviet experts, the 12 tubes specified by the initial design were blocked by reinforced concrete during construction. By 1967, each and every one had to be reopened at a cost of 10 million yuan each.”

Following the June 1957 meeting, Mr. Huang was labelled a “rightist” and forced to work as a labourer at the Miyun reservoir in Beijing. Later, during the Cultural Revolution, he was sent to work near the Sanmenxia dam, where, Ms. Shapiro writes, “he laboured by day and investigated siltation problems by night.”

Reflecting years later on the Sanmenxia debate, Mr. Huang told Ms. Shapiro: “I have no regrets about what I did. … I was certain there would be trouble [with the dam], but no one dared agree with me. In fact, it was clear that I was right as early as 1964, two years after the dam was completed. A town was completely flooded because of the silt.”

In an article contrasting the roles of Mr. Zhang and Mr. Huang, expatriate Chinese scholar Qu Wuxi concurs: “Less than two years later, all [Huang Wanli’s] predictions about Sanmenxia came true. About 1.5 billion tons of silt were deposited behind the big dam. And the riverbed at Tongguan, 100 km upstream of the dam, was elevated by 4.5 metres [due to sedimentation], leading to severe salinization of the Guanzhong plain and posing a direct threat to Xian, the capital of ancient China.”

By the third year of operation, the reservoir had accumulated about five billion tons of sediment, adjacent farmland was waterlogged, and Shaanxi province, where Xian is located, appealed directly to Mao Zedong for help. “When faced with the reality of the situation,” Shang Wei writes, “Mao became very upset and told [premier] Zhou [Enlai]: ‘If nothing works, then just blow up the dam.'”

Sanmenxia had to be rebuilt at enormous cost. In fact, Ms. Shapiro writes, “the dam was repeatedly reconstructed with tubes at the base to increase silt discharge capacity, but in 1969, again there were floods in Xian. Eventually, the dam was so pierced with holes that it became virtually worthless for either flood control or electricity generation. Today, the Yellow River runs as muddy as ever … while the dam’s legacies of increased turbulence, frequent dike collapses, sediment buildup, and ecological changes continue to cause problems for local people. …”

The dam caused great human suffering. More than 400,000 people were forced to move from the fertile river valley to barren, inhospitable land in two of China’s poorest provinces, Ningxia and Gansu. Because of the problems with the dam, the water level in the reservoir was kept lower, and less land was inundated, than planned. Many of the farmers who had been relocated unnecessarily petitioned for years to return to their old homes. After a quarter-century of struggle, the migrants did finally win back about a third of their land. But they returned to find much of the soil was now unsuitable for growing crops because of salinization and other environmental problems caused by the dam.

In his autobiography posted on the Web site of the Chinese Academy of Engineering, Mr. Zhang expresses regret about his role in the Sanmenxia fiasco. “I have been deeply tormented by a guilty conscience over my part in building the Sanmenxia dam on the Yellow River,” he writes.

“In the beginning, I argued that to prevent a buildup of sediment, it was crucial to release floodwater to wash the silt out of the reservoir. But I failed to stick to my guns on this, and instead took part in sealing off the outlets at the bottom of the dam through which sediment would have been released. As a result, the reservoir silted up rapidly and dramatically, posing an extremely serious threat to the Guanzhong plain, and especially the city of Xian.

“We paid a high price for the mistake, and had to open up the outlets again and build new tunnels under the dam to flush out the sediment. Unfortunately, doing so resulted in another unexpected consequence: a substantial reduction of generating capacity,” laments Mr. Zhang, whose career, nonetheless, never missed a beat.

When the idea of building a large dam on the mainstream of China’s other important river, the Yangtze, was being discussed in the 1930s, Mr. Zhang was initially opposed. In his online autobiography, he recounts taking the U.S. Bureau of Reclamations chief designer, John Savage, on a tour of the proposed location. Mr. Savage, who had designed major U.S. dams such as the Hoover and Grand Coulee, “regarded the Three Gorges as an excellent site for building a big dam,” Mr. Zhang writes. “After his return to the United States, [Mr. Savage] recommended to the American government that it assist in the construction of the Three Gorges dam by providing financial and technical assistance. The Guomindang government was keen on the idea and asked me to return to China to take part in the survey and planning work for the proposed project.

“But I didn’t think that building such a huge dam was a good idea,” Mr. Zhang continues. “Given China’s conditions at the time, the dam was too big. And even if we were able to build it, we would have no customers for the electricity. More importantly, I felt there was a danger the United States would be able to control China’s economy by building the Three Gorges dam, which would have harmful consequences for the country as a whole.

“I wrote three letters to the Resource Commission, urging caution. But the government did not heed my concerns and instead asked me to return to China as soon as possible. So I went back and devoted myself to the project for a while. But very soon everything stopped, and the American experts withdrew from China because of the war. On the one hand, I was happy to see the project abandoned. On the other hand, I felt somewhat uneasy because it was me who had invited Dr. Savage to get involved in the Three Gorges project in the first place.”

Mr. Zhang’s autobiography then leaps from describing these early misgivings to celebrating his later role as one of the chief architects of the Three Gorges dam. “I have done a lot of work on the Three Gorges project, including survey, planning and design,” he writes. “With great vigour and enthusiasm, I have insisted that the Three Gorges dam should go ahead as soon as possible because of its great socioeconomic benefits.

“We have no difficulty building the big dam in terms of our expertise in science and technology. I believe that local people’s standard of living will be improved through the policy of ‘resettlement with development.’ At the same time, it is very important to pay attention to environmental protection and try to keep harmful impacts to a minimum. I have no regret about my choices and decisions because what I have done … is good for the country and for the Chinese people.”

Mr. Huang, meanwhile, drew on his own long experience with large dams “to remind policymakers not to repeat [with Three Gorges] the mistakes of the past, where money was wasted, millions of people adversely affected, and the environment destroyed,” writes journalist and environmentalist Dai Qing. Mr. Huang warned that the tail end of the dam’s reservoir, at Chongqing harbour, would silt up with coarse pebbles, causing more frequent and severe flooding in the densely populated region. He also said the project would become a bottomless pit for public funds, and that the prospect of successfully resettling close to two million people was doomed to failure.

Mr. Huang never relented in his campaign to petition the government and to write about the dam. To his regret, his articles were never published and nobody paid attention to his petitions – with one notable exception, Ms. Dai recalls. In his 1995 letter to U.S. president Bill Clinton, Mr. Huang expressed concern that if the Three Gorges dam were built, Chongqing harbour would become choked with sediment. He predicted that within a few years of the dam’s completion, it would have to be dynamited in order to restore the river.

Responding from the White House, Mr. Clinton wrote: “Thanks so much for writing to me. Your thoughts are welcome, and they will be considered carefully.” A few months later, the National Security Council recommended that the U.S. government not “align itself with a project that raises environmental and human rights concerns on the scale of the Three Gorges.” The U.S. Export-Import Bank decided not to provide financing for the dam.

“Huang Wanli is a courageous man,” Shang Wei writes. “For over forty years he was virtually alone in his opposition to the Three Gate Gorge [Sanmenxia] project, and to the planned Three Gorges project on the mainstream of the Yangtze River. He has been publicly attacked and isolated for his views, but he has never compromised.”

Because of those unswerving views, Mr. Huang was not permitted to teach in China for four decades – until 1998, when at the age of 87 he was finally allowed to lecture postgraduate students at Qinghua University. On the day of his first class, he entered the lecture hall wearing an all-white Western suit and a red tie – the colour red in China symbolizing joy and a festive occasion. After three happy years of teaching, Mr. Huang died last August at the age of 90.

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This article draws on Dai Qing’s obituary of Huang Wanli; Zhang Guangdou’s autobiography on the Chinese Academy of Engineering website; “A Lamentation for the Yellow River,” Shang Wei’s chapter in The River Dragon Has Come! (Dai Qing, ed.); Judith Shapiro’s book Mao’s War against Nature; “Two Chinese water-resource experts,” an article by Qu Wuxi posted on the U.S.-based website Democratic China (Minzhu zhongguo); and an article on the Sanmenxia migrants posted on the same site by the U.S.-based writer Zheng Yi.