Geólogos chineses alertam para falhas geológicas na construção de barragens no rio Nu
At fault on the Nu River
China Dialogue, March 22, 2011
As China gears up for a hydropower push in its earthquake-prone south-west, it should pause to consider events in Japan, two geologists tell Liu Jianqiang on World Water Day.
“You could say Japan is on the side of a knife, while the Nu River is on the blade.”
With the ongoing crisis at its earthquake-damaged Fukushima nuclear plant, Japan is paying a heavy price for ignoring “large-scale environmental evaluations”. This is the assessment of two prominent Chinese geologists, Xu Daoyi and Sun Wenpeng, who told chinadialogue that the incident holds important lessons for China.
The two experts argue that the Japanese authorities underestimated the potential impact of deep-ocean faults and earthquakes on power plants. As a result, they failed to locate their atomic energy facilities on the country’s less vulnerable west coast and, ultimately, to avoid the radiation crisis the world has watched unfold over the past week.
There are worrying parallels in China, said Xu and Sun. But rather than focusing on the nuclear industry, their gripe is with their country’s hydropower sector – and, more specifically, the controversial plans to build a cascade of dams on the Nu River, China’s last great waterway without large-scale hydropower and the focus of an animated public campaign.
Xu, a retired researcher from the China Earthquake Administration’s Institute of Geology, and Sun, a former employee of the China National Nuclear Corporation (CNNC), who was once in charge of evaluating the nation’s uranium resources, have written to the Chinese premier, Wen Jiabao, setting out their concerns. In their letter, they write that the risks of building dams on the Nu – a plan that was shelved in 2004 following a public outcry, but has recently been revived – have not been fully assessed. “We are extremely troubled by this,” they add.
Xu spent 40 years working in the field of earthquake prediction [Editor’s note: While earthquake prediction is a controversial or even discredited field of science in many parts of the world, in China it has long been part of the national earthquake administration’s programmes on quake monitoring and disaster prevention, although reports suggest it may soon be phased out.]. Sun specialises in structural geology and, before his retirement, worked at CNNC’s Beijing Research Institute of Uranium Geology. They argue that, as the Nu River lies on a structural fault at risk of earthquakes, there are enormous risks involved in building dams there – and that pressing ahead with these plans flies in the face of common sense.
When Xu and Sun first heard about proposals for large-scale hydropower development on the Nu River — which starts high up on the Tibetan plateau and flows through south-west China and down to the Indian Ocean — they were shocked. “Tectonic movement in [Yunnan’s] Three Parallel Rivers area is stronger than anywhere else in the world– how can they build a cascade of dams here?” asked Sun.
The pair pointed to three major risks. First, tectonic activity in this region means earthquakes are both strong and frequent. Second, other geological events such as mudslides are common. Third, tectonic movement has been strengthening: earthquakes and other disasters are becoming more frequent in the region, claim Xu and Sun, and the combination of climate extremes, tectonic and seismic activity is increasing the risks of a major disaster.
Debate over dams on the Nu River has been raging for eight years. The first report on hydropower development on its lower and middle-reaches recommended building a cascade of 13 dams, with generating capacity of 21.32 gigawatts. But in 2004, following a public outcry, Beijing imposed a dam-building moratorium on the river. Then, in January this year, Shi Lishan, deputy head of the New Energy and Renewable Energy Division of China’s National Energy Administration, said: “My belief is that development [on the Nu] is a must.”
This was the first time the National Energy Administration had made clear its views, and appeared to indicate that hydropower in China is about to enjoy a “great leap forward”. However, the official pronouncement has drawn fierce criticism from Chinese NGOs, the media and the public. [See chinadialogue article “Hydropower’s Green Excuse” for more detail on this].
However, Xu and Sun’s statements mark the first time in eight years that geologists have publicly expressed doubts over the plans. In their letter to Wen Jiabao – a geologist himself, who like them graduated from the China University of Geosciences — Xu and Sun write: “No fixed steel and concrete dam can withstand the shearing movement of the Nu River fault, nor can anyone prevent the huge mountainside collapses, landslides and mudslides that still happen on the banks of the river.”
Sun and Xu say that there is no precedent for building such a large hydropower scheme over an active fault, and that we should not be lured into complacency by China’s recent successes in the construction of large dams. The unusual geology of the Nu River means that the risks here are greater than elsewhere: the fault that forms the Nu River is still active. And, if built, the cascade of dams will run directly across it. “It’s like building on the blade of a knife – we are taking a huge risk,” said Sun.
Even the geologists who drew up the plans for the Nu River dams agree, according to Xu and Sun. Everyone admits that the geological structure of the lower and middle-reaches of the Nu River is complex. The Nu River fault is the major geological feature of this stretch of the river and is the central factor in determining dam location and safety. “But we feel the planners weren’t wary enough of those geological hazards, with risk evaluations mainly, or even only, looking at the factors affecting individual dams – these were separate ‘micro-evaluations’ [and not, broader ‘macro-evaluations’],” said Xu.
Xu said that over the past two centuries, and particularly in the last 60 years, western China (and especially the south-west) has been hit by frequent earthquakes: in 1950, an 8.6-magnitude earthquake in eastern Tibet, near the Nu River; in 1976, an 7.3-magnitude quake in Longling, Yunnan; in 1988, earthquakes measuring 7.4 and 7.2 on the Nancang River and at Gengma; in 1995, an 7.3-magnitude quake on the China-Myanmar border; and in 1996 one measuring 7.0 in Lijiang. All of these are on or near the Nu River.
According to Xu, there has been a clear increase in the number of strong earthquakes in the south-west of China over the last century, a fact that should not be ignored when evaluating regional geological stability and earthquake trends. To date, he has not encountered any geologist or seismologist who does not expect a major earthquake on the Nu River during the twenty-first century.
Both Sun and Xu believe that earthquake damage is not limited to the epicentre: its extent is related to the strength of the quake, and the stability and integrity of the surrounding geology. Even a large earthquake far away from the Nu River could trigger local disasters, such as mountainside collapses, landslides and mudslides.
Xu said that one possible scenario is that a failure at one dam causes a chain reaction in dams further downstream. If one hydropower plant is damaged, particularly if it is located upstream, hundreds of millions of cubic metres of water, carrying large quantities of mud and rock, would rush down the straight, narrow and steep river valley. The damage would be devastating. “There wouldn’t even be any survivors to rescue,” said Sun. “And it’s an international river – if the disaster were to extend to countries downstream, I’m afraid China could not cover the costs.”
Another risk is that hillsides could collapse into the reservoirs, creating huge waves that threaten the dam, or forming blockages that will impact on local hydrology and on the lower reaches of the river. The huge mudslide that hit Zhouqu in Gansu, north-west China, last year – and which many have blamed on human development in the area – should be an important lesson for those considering hydropower construction on the Nu River.
Perhaps in response to the concerns raised by these two geologists, two long-standing supporters of the Nu River plans – the China Society for Hydropower Engineering and the Chinese National Committee on Large Dams – held a meeting in Beijing on March 6, to which they invited hydropower and geological experts. Speaking at the event, Xu Xiwei, head of the China Earthquake Administration’s Institute of Geology, said: “Japan lies where the Pacific plate pushes west – why can they build dams there, but we can’t do the same here?”
But Sun told chinadialogue: “He’s mixing things up. You can’t compare Japan and the Nu River.” Japan lies on one side of a fault, while the Nu River runs through the fault itself, he explained. “You could say Japan is on the side of a knife, while the Nu River is on the blade.”
In fact, recent events in Japan demonstrate just how serious the issue is for China, added Sun. The Fukushima nuclear plant wasn’t built on the fault: the problems were caused by a chain of events triggered by the tsunami. If anything happened to a dam on the Nu River the consequences could be even worse.
“Japan took a gamble by building the plant there, and lost. The officials all say the disaster could not have been predicted. In fact, the authorities were warned about the risk – and they chose to go ahead anyway.”
Liu Jianqiang is the Beijing-based deputy editor of chinadialogue.
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