Dams and Landslides

FEATURE: Three Gorges dam authority suspends reservoir filling

(November 27, 2008) Mountains of floating garbage, geological problems, and stranded cargo ships prompted China’s Three Gorges dam authority to suspend filling the dam’s reservoir to its final height last month, according to the popular magazine South Weekend (Nanfang Zhoumo).

In early November, with just two metres to go before reaching a final reservoir height of 175 metres, the State Council’s Three Gorges project construction committee ordered a stop to the trial filling that began in late September. The decision, according to South Weekend, was prompted by three serious problems – a massive surge of floating garbage on the reservoir surface, hundreds of landslides and subsidence problems along the reservoir’s unstable shoreline and, most importantly, stranded cargo ships downstream of the dam caused by low water levels during reservoir filling.

Read the full translation of the South Weekend article below:

A big test for Three Gorges to be filled to 175 metres
South Weekend (Nanfang Zhoumo) by Chen Jiang, November 27, 2008

In early November, the State Council’s Three Gorges dam authority, known as the Three Gorges Project Construction Committee (TGPCC), issued a notice [to the dam operators] to stop filling the Three Gorges reservoir. Based on official data released by the Three Gorges Corporation, the water level at the dam site had reached 172.47 metres before the suspension with only 2.53 metres to go for the final reservoir height (Normal Pool Level) of 175 metres.

This first trial filling to 175 metres was suddenly and temporarily suspended for several reasons: an unexpected surge of garbage on the reservoir surface, a growing problem with geological disasters, and more importantly, the interruption of shipping on the main channel of the Yangtze below the dam.

Unexpected surge of floating garbage: a serious challenge

According to statistics released by the Chongqing municipality in late November, about 40,000 tonnes of floating garbage has been collected from the reservoir since filling began at the end of September. In total, the collection effort has required 33,895 man-hours and 7,687 boat-hours.

In Wanzhou, a mountainous city at the heart of the Three Gorges reservoir, Liu Gujun and his team set an astonishing record collecting as much as 200 tonnes of floating garbage in a single day. Before the latest filling period, Liu Gujun and his team were already struggling to deal with the problem of floating garbage around Wanzhou and Yunyang. But when filling began on September 28, they were shocked by the surge of garbage that appeared all of a sudden and was everywhere along the reservoir surface, Liu Gujun told South Weekend.

With 51 boats for collecting garbage, Liu Gujun and his team were fighting day and night on the river but had difficulty getting the job done. With helplessness written on his face, Mr. Liu admitted his work was not an offensive but a defensive battle against the floating debris.

Liu Gujun described his shock one day in particular, October 17, when he woke up in the morning and went down to the riverbank to find a huge mound of floating garbage motionless on the river surface because of the south wind. Just the day before, he had checked the situation along the river shore and it was not that serious. “As you see now,” said Mr. Liu, “the river looks cleaner but actually its self-purification capacity is not as good as before the dam. The real problem is when the river is motionless, almost still.”

Pointing to the centre of the river, Liu Gujun said he and his team must continue collecting garbage because there is a pipe drawing water from the reservoir to the Wanzhou waterworks, which provides water to the whole city. “So as you can see, how can we stop collecting [the floating garbage]?” Mr Liu asked.

An official at the Environmental Protection Bureau of Wanzhou told South Weekend that the Wanzhou government has invited a Tianjin-based institute to design a large garbage treatment plant for the city. But he doubted building a single garbage treatment plant at Wanzhou would do anything good because there are no such facilities in all the towns and townships upstream along the reservoir. As he explained, there is a mountain of garbage upstream, so Wanzhou is dealing with the garbage “transferred” from upstream, especially after rainstorms and floods, and when the reservoir is filling.

A growing problem with geological disasters

Floating garbage isn’t the only annoying problem to arise while the reservoir was filling to 175 metres. Not far from the wharf at Wanzhou where Liu Gujun and his team park their boats, a road along the reservoir shore has cracked and the ground underneath is sinking. The road condition appears to be getting worse all the time which has prompted local officials to monitor the situation.

Geological problems like this are not uncommon in the Three Gorges reservoir area. According to a joint report by the Nanjing Institute for Geography and Lakes of the Chinese Academy of Sciences and Changjiang (Yangtze) Water Resources Commission, landslides and bank collapses have been identified at 4,719 places in the reservoir area. Of these, at least 627 are associated with filling the reservoir.

Interrupted shipping below the dam

A third serious problem has to do with shipping in the river channel below the dam. Impounding water behind the dam means that water does not get discharged, causing water levels in the main channel of the Yangtze downstream to drop. This has a direct impact on water supplies and the shipping business in the main channel and tributaries downstream.

To prevent incidents of stranded ships during the reservoir filling period, the Yangtze marine department issued a notice asking ships on the middle Yangtze below the dam to control the draught of their boats. [TGP Editors’ note: The Maritime Dictionary online defines draught as “the vertical distance measured from the lowest point of a ship’s hull to the water surface.”] During the filling period, ordinary boats were directed to keep their draught under 2.7 metres, while boats loaded with dangerous cargo were directed to keep theirs under 2.6 metres. Under normal conditions, a freighter loaded with 3,000 tonnes of cargo is generally required to keep a draught of at least 3 metres.

Based on Hubei province media reports, the water level at the port city of Chenglingji, [downstream of the dam] the most important water-land transportation hub in-between Wanzhou and Wuhan, dropped sharply during the filling period to just three metres deep in places. According to the river administration of Chenglingji, “The incidents of ships stranded on the Yangtze occurred almost every day” during the last half of October.

Also affected by low water levels was the so-called “vital passage” of the middle Yangtze near the county seat of Jianli in Hubei province [downstream of the dam]. The water level there dropped suddenly from a depth of eight to three metres after filling began. According to local media reports, four boats got stranded between October 17 and 20. Then on October 20, all shipping was stopped for four hours while the waterway was dredged. A few days later, more boats were stranded in the same section on October 23, 24, and 25.

Since October 28, the Three Gorges Corporation [the dam’s operator] started releasing more water from the reservoir to raise water levels in the river section immediately below the dam. On October 31, the volume of water released was further increased to 8,700 cubic metres per second, which caused a rapid rise in water levels in both the main channel and tributaries downstream. This greatly improved shipping conditions and the water supply in downstream cities, particularly Changsha in Hunan province, local media reported.

Finally in early November, the Three Gorges Project Construction Committee issued a notice to stop filling the Three Gorges reservoir, putting an end to the trial filling to its maximum height of 175 metres. Currently, the water level at the dam site is about 172 metres, so the goal of filling the Three Gorges reservoir to the final height (Normal Pool Level) of 175 metres [by November 2008] has not yet been achieved.

[TGP Editors’ note: We checked the website of the Three Gorges Corporation on December 2, 2008: the water level was 170.42 metres at the dam site at 2 pm on Dec 2nd, Beijing Time.]

Chen Jiang, South Weekend (Nanfang Zhoumo), November 27, 2008

Translation by Mu Lan, Three Gorges Probe

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