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Consider, the Chinese knowingly built these damns with poor quality concrete. Those troops are not at the damn to repair it IMHO. The troops are there to keep the journalists away from the awful truth that the dam is crumbling. If it hasn’t washed out already. God Help Them Lord for they know not what they do! Amen

The High Cost of Geological Disasters in China

Posted by chinaview on February 24, 2007

by Fan Xiao, translated by Three Gorges Probe, January 29/2007- (cont’d)

The high cost of geological disasters

The river valleys in which most of China’s big dams are planned, under construction or already built — including the Min, Dadu, Yalong, Jinsha, Lancang-Mekong and Nu — are located in the transition belt between the Qinghai-Tibetan Plateau and the Yunnan-Guizhou Plateau and Sichuan Basin. The geology in this area is unstable, and geological disasters are frequent.

Due to the dramatic variations in topography and landscape, regions such as this are seen, both inside and outside China, as holding tremendous potential for hydropower development. But at the same time, the risk of geological disasters is particularly high, and a number of hydropower projects have been built in this region of southwest China without due regard for the danger.

There are several well-known earthquake zones and seismically active belts in the region, and an average of one quake registering at least 6 on the Richter scale strikes every 10 years. This is also the region of China that is most plagued by landslides, riverbank collapses and mud-rock flows.

For example, in 1989, during construction of the Manwan dam on the Lancang (Mekong) River in Yunnan province, excavation work on the left bank triggered a massive riverbank collapse, which cut off a road on the top of the dam, brought the construction work to a halt and added 140 million yuan (US$17.5 million) to the cost of the project. Since 1993, when the first Manwan generators went into operation, more than 100 riverbank collapses and landslides have been caused by the big changes in water level during the regular operation of the reservoir.

In March 1995, for instance, 51 riverbank collapses and landslides occurred over the course of one week in Jingdong county alone due to the sudden drop of water level from 991 metres to 940 metres. According to official statistics, 2,958 local people had to be resettled for a second time because of geological disasters triggered by the dam — almost as many as had to be relocated for the dam in the first place (3,042).

In 1996, the Geheyan dam was completed on the Qing River, a tributary of the Yangtze below the Three Gorges. When the Geheyan reservoir was filled for the first time in 1993, rising from 132 metres to 200 metres, deformations began to appear in the Maoping landslide located 66 kilometres upstream of the dam. The landslide had been stable for years and had shown no signs of deformation before the filling of the reservoir.

But now, in the past few years, the huge Maoping landslide, which has a volume of 24 million cubic metres, has started slipping again. If it were to slide into the river, the Qing would be completely blocked and make another big dam upstream unworkable. This is the 233-metre-high Shuibuya dam, currently under construction 90 kilometres upstream of Geheyan and scheduled to be completed in 2008.

In 2001, at the Zipingpu dam site on the Min River, excavation work on the slopes, combined with several days of rain, triggered large-scale landslides and mud-rock flows, blocking a national highway and causing other economic losses.

Dam-induced seismicity is another major problem. As many as 15 earthquakes triggered by dams have been recorded in China.

One of the most serious such tremors occurred near the Xinfengjiang reservoir on the Dong River in Guangdong province. Seismic activity was detected just a month after the reservoir was filled in 1959. And then, on May 7, 1962, a powerful earthquake registering 6.1 on the Richter scale shook the area, with the epicentre only 1.1 kilometres upstream of the dam. The quake killed six people, destroyed 1,800 houses and caused an 82-metre-long crack to open in the structure of the dam, rendering it unworkable. The incident was ranked as one of the world’s six most powerful earthquakes above 6 on the Richter scale that have been triggered by dams.

Two big earthquakes, also above magnitude 6, were reported in Dayao, Yunnan province, in July and October 2003. The tremors damaged 54 large and medium-scale reservoirs built on tributaries of the Jinsha River. Many of the structures developed cracks and began to leak water, forcing the evacuation of people living downstream.

When a dam is being planned and built, the potential impact of seismic activity is considered, and measures to protect the dam are proposed. However, in a geologically complex area prone to disasters, such as southwest China, this does not mean that the dam will be safe. And this does not mean that the reservoir area or the region below the big dam will be safe.

In China, both the feasibility study and environmental impact study for a dam will focus mainly on a geological assessment of the proposed site and the foundation on which the powerhouses will be built. Little attention will be paid to the valley as a whole where this development will take place.

Furthermore, even when a more comprehensive geological assessment of the region is made, the costs of the potential geological disasters are not often taken into account, either in the cost-benefit analysis or the decision-making process. (END)

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