Dams and Landslides

Holding back the Yangtze – for now

(August 31, 2010) Thirty-five years on from the horrific Banqiao Dam disaster, heavy flooding is causing some Chinese to wonder whether the new Three Gorges Dam is an engineering triumph or a tragedy waiting to happen, writes CLIFFORD COONAN in Beijing.

THE THREE GORGES DAM is one of the engineering marvels of the world, and to stand on top of the barrier holding back China’s mighty Yangtze is an awesome experience.

The dam is 2.3km long and 185m high, with a five-tier lock system that helps give ships from booming coastal cities such as Shanghai better access to central China. On the two sides are 26 hydropower generators transforming the surging waters of the 6,000km river into electricity.

The dam is supposed to represent a triumph of technology over nature, but the heavy rains of this summer, which triggered landslides and flooding all over China, killing thousands and causing billions of euro in damage, have also raised concerns about the dam’s ability to fulfil its primary function and end centuries of flooding on the Yangtze.

A year since it became fully operational the €18 billion dam, whose construction flooded 116 towns and hundreds of ancient historical sites and led to the relocation of 1.4 million people, is a source of considerable pride in China, a symbol of the country’s development into one of the world’s great nations, the second biggest economy on earth.

The Chinese government insists that the dam is necessary. The Yangtze regularly bursts its banks, and nearly a million people have drowned in floods in the past 100 years or so. The dam is supposed to stop this happening.

It is said that the dam reduced the impact of the recent flooding by holding back about 31,000 cubic metres of floodwater per second, and discharging the rest. But the official tone has become a lot less certain. A report released in June 2003 claimed that the dam could control the worst flood in 10,000 years. Four years later that claim was down to the worst flood in 1,000 years, and in 2008 it was revised to the worst in 100 years. Officials are conceding that the dam is not invulnerable.

Zhao Yunfa, deputy director of China Three Gorges Corporation’s cascade dispatch centre, told local media that the safety of the dam would be threatened if floodwater rushed through at more than 122,000 cubic metres per second. “The dam’s flood-control capacity is not unlimited,” he said.

Water levels at the world’s largest hydroelectric project have been alarmingly high for weeks, from record rains in its upper reaches. Water flowed into the reservoir of the dam at a rate of 70,000 cubic metres per second on July 20th.

The dam reservoir’s maximum depth is 175m; a flood alarm is sounded once water passes 145m. This summer the level rose to an alarming 158m, and last week it hit 152m. That’s getting too close for comfort. In the past few days authorities have stopped shipping through the dam, fearful of more flood peaks.

The worst days have seen 3,000 tons of garbage flow into the reservoir every day, causing a huge floating island of green plastic bottles, branches, carrier bags and white Styrofoam lunch boxes, debris washed down the mighty Yangtze from the worst rainstorms in decades. The trash covers 50,000sq m of water and is 60cm deep – thick enough to walk on.

“The large amount of waste in the dam area could jam the lock gate of the Three Gorges Dam,” Chen Lei, a senior official at China Three Gorges Corporation, told local media. “Such a large amount of debris could damage the propellers and bottoms of passing boats. The decaying garbage could also harm the scenery and the water quality.”

Environmentalists have long been critical of the project, saying that silt trapped behind the dam is causing erosion and warning that the dam’s reservoir will turn into a cesspool of raw sewage and industrial chemicals backing on to the city of Chongqing.

There are also fears that global warming could lead to worse flooding than expected, with melting glaciers and more rain in southwest China leading to unusually high water.

“I am worried about the consequences of the Three Gorges Dam personally, since I have already experienced major climate change in the past few years in my city, and also experienced the floods this summer,” says Gu Haoteng, who works in environmental protection in Chongqing. “I’m not worried about Chongqing being flooded, but I believe that anything bad you do to nature it will ask you to pay back one day.”

Chen Lina lives in Wuhan, in the central province of Hubei, downriver from the dam. “What I’m most worried about is what happens downriver from the Three Gorges Dam during flooding, because Hubei would be the first victim. Another thing is climate change and ecosystem changes,” he says.

The most famous opponent of the dam in China is the environmental activist and journalist Dai Qing. She believes the warnings of independent analysts were ignored and that the dam is an expensive folly. Her book criticising the project, Yangtze! Yangtze! , earned her 10 months in a maximum-security prison, during which she was threatened with the death sentence. “So what indeed can this big project, which took 20 years, moved millions of civilians, submerged 470,000 units of land and cost billions, do in the face of this year’s flooding on the Yangtze River?” she asks in a recent blog posting.

Dai Qing takes issue with the government’s claims about the dam’s ability to control flooding. She believes the storage capacity of 22.15 billion cubic metres is a design figure calculated 20 years ago. “Since then there have been a lot of changes in the area, which have altered this storage capacity,” she says.

She also wonders whether, if the water was to rise above 175m, the city of Chongqing would be in danger.

Zhang Yulong, a long-time Chongqing resident, believes the government did a lot to balance the advantages and disadvantages of the Three Gorges Dam project before deciding to build it, calculating, for example, how much Chongqing would benefit from improved river transport and power generation.

“It’s a choice between short-term sacrifice and long-term profit,” he says. “I hope the decisions the government made were right. But what I am worried about most is the safety of the dam itself. I mean, if it is proved to be another tofu project after many years, that would be a real disaster for the whole country. I cannot imagine what would happen if the dam collapsed like the disaster in 1975 in Henan.”

Doomed dam: The world’s worst man-made catastrophe

The Banqiao Dam, on the Huai River in Henan province, was supposed to be an “iron dam”, a barricade that could not be broken and could withstand the kind of flood that comes only every 1,000 years.

Instead, 35 years ago this month, it gave way during Typhoon Nina, and hundreds of thousands of people are believed to have perished as a result of the world’s worst man-made catastrophe.

Record rainfall meant that reservoirs had filled to capacity. Days after the storm, river levels were rising steadily. On August 8th the water level on the smaller Shimantan Dam, upstream, rose 40cm above the top of the dam and emptied 120 million cubic metres of water within five hours.

Half an hour later the Banqiao Dam collapsed, releasing a wall of water six metres high and 10km wide.

In a dramatic account in Dai Qing’s book The River Dragon Has Come!, an older woman who was helping a group of volunteers trying to stop the dam collapsing suddenly shouted: “Chu Jiaozi .”

In all, 62 dams collapsed, and the flood spread over a million hectares of agricultural land in Henan. While tens of thousands of people died directly because of the flooding, many more died because of the subsequent epidemics and famine. Nearly six million buildings collapsed.

Clifford Coonan, Irish Times

Read the original article here.

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