Peter Huston
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Eight large "quake lakes" in Sichuan threaten remaining villages
http://news.xinhuanet.com/english/2008-05/23/content_8231864.htm
Special report: Strong Earthquake Jolts SW China
BEIJING, May 22 (Xinhua) -- Of the 34 "quake lakes" found in Sichuan Province, formed by landslides that blocked rivers, eight hold more than 3 million cubic meters of water, adding potential danger for the people who have already lost much to the earthquake.
According to remote sensing information from the air and space, as well as field observations from experts, a quake lake only 2.6 km from Beichuan County, which was devastated by the 8.0 magnitude earthquake on May 12, had doubled between May 14 and May 18 to 150,000 square meters in surface area. Xuanping and Zhangjiaba villages, which were near the lake, are flooded.
To make matters worse, the Chinese National Meteorological Center (NMC) predicted that rains might sweep the quake-hit regions of the southwest next week and raise the water level of quake lakes.
A quake lake once burst and caused a major disaster after an earthquake that hit Maoxian County in 1933, said Yin Yueping, deputy chief engineer with China Geological Survey (CGS), adding that they had been monitoring these newest lakes since the quake.
Information on all 34 quake lakes has been sent to quake control and relief headquarters, the Ministry of Water Resources and the government of Sichuan Province for reference.
According to Yin, efforts are being made to evacuate people living downstream of the lakes. But he did not reveal the exact population to be evacuated.
Zhu Bing, deputy head of the water resources authority in Sichuan Province, said the province has formulated emergency response plans, including evacuating people to safer places when necessary and blasting or digging of sluices to discharge water.
The Ministry of Land and Resources and the Ministry of Water Resources jointly sent experts to check and assess the condition of the lakes. The experts departed from Beijing for the sites on Thursday.
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"Quake lakes" on China river to be fixed; thousands evacuated
www.chinaview.cn 2008-05-21 23:11:56 Print
Special report: Strong Earthquake Jolts SW China
http://news.xinhuanet.com/english/2008-05/21/content_8222971.htm
MIANYANG, Sichuan, May 21 (Xinhua) -- Water resources officials working in China's quake-stricken areas said Wednesday they have made plans to repair damage to a river that threatens to burst.
The upper stream of the Qianjiang River near Beichuan County was damaged in the May 12 earthquake, forming "quake lakes" as water was shoved from its bed by rock and mud slides sent off by the earthquakes.
On Saturday, thousands of people were evacuated from Beichuan as officials warned of flood risks.
Officials from the Ministry of Water Resources, the Yangtze River Water Resources Commission, the Hydro-power Plant Branch of the Armed Police and Sichuan provincial officials discussed plans to address the risks in an emergency meeting on Wednesday afternoon.
Jiang Jianjun, a Ministry of Water Resources official, said a general plan was being drawn for the treatment of all the quake-formed lakes.
Blasting or digging of sluices would be carried out to discharge flood for big such lakes after residents were evacuated safely, according to the plan.
Small quake lakes would be monitored around-the-clock to assess their flood risks.
Light-weight cranes, bulldozers and trucks would be brought in first by helicopter to dig sluices on the embankment, said Zhang Jian, chief of the water resources brigade of the disaster relief headquarters of the Mianyang City, which administers Beichuan.
But before that can happen, a parking apron must be built on the river embankment so helicopters can land, said Zhang.
"All of the roads have been destroyed, and it's not possible at this stage to get the equipment in by road," he added.
Zhang said the lake is stable now but repairs should be done quickly due to imminent danger. "The risks increase by every meter that the water level rises. Downpours last night raised the water level by 3.7 meters."
Further, workers must disinfect the county before work begins on the embankment, where animal carcasses were seen on Wednesday.
Zhu Bing, deputy head of the provincial water resources department, told a news conference on Wednesday that there are about 33 such quake lakes in nine counties in Sichuan.
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May 21, 2008
China works flat out to prevent dam flood
AFP/Getty Images
http://www.timesonline.co.uk/tol/news/world/asia/article3972785.ece
Earthquake survivors flee in a speedboat from a landslide set off by an aftershock in Yingxiu, Sichuan Province
Jane Macartney and Hattie Garlick
Chinese engineers are working round the clock to try to stop thousands of people from being flooded out by water in a dam that was created by landslides during the earthquake, The Times has learnt.
The swelling lake that has risen to 70m (230ft) would threaten, if it burst, the five million residents of Mianyang county, home to the second-biggest city in southwestern Sichuan province. It is expected that the water will be released to avert a collapse.
China has pledged to save every life it can, mobilising 130,000 troops and countless medical staff and helpers nationwide. Two people were pulled out alive from the rubble yesterday — a 60-year-old woman, who survived by drinking rainwater, and a man rescued from a flattened power plant.
David Petley, Wilson Professor in Hazard and Risk at Durham University, said that if the water were to seep through and erode the barrier, it could send bricks, trees and other debris downstream. "You can't be sure that the town below would be destroyed, but it would certainly be a very dangerous place to be," he said.
One plan is to build up earth barriers halfway across the Beichuan river, at several points downstream from the reservoir. These barriers would divert the water, slowing its flow and reducing the danger to communities in its path. Once these were ready, some or all of the water could be released over the next day or two, possibly by blasting away part of the landslide.
Professor Petley said that the usual method of breaching a dam, familiar to military engineers, would be to build a channel across the top, starting from the dry side and excavating towards the water. "The channel has to be lined with big rocks to stop the water corroding it and causing a huge flood, but the key thing with this method is that only the water at the top of the lake will flow out and you control the flow."
More than a thousand dams of different sizes lie in the area hit by the 8.0-magnitude earthquake. Eleven teams of about ten specialists each have been sent to carry out checks on all of the dams. Another six teams have been assigned to monitor lakes formed by landslides, which have blocked rivers in at least 21 places.
More than 2,000 people were moved at the weekend from a village in Hongyuang township after the blocked Qingzhu river burst its banks and began flooding their homes.
At one dam in Fuxing Township, a team of engineers from northeastern Liaoning Province was using lorries and diggers to shore up a small reservoir that had sprung a leak during the tremor.
Dai Yuxin, leading the team, told The Times: "It only looks simple. By the morning we will have moved in 8,000 cubic metres of earth. It is as if we are building a second dam here."
His team had driven for six days across China to reach the earthquake area. "If the dam bursts then it would be like another earthquake for the people here," he said. Officials have already helped the farmers downstream to bring in their crops — just in case.
Gu Junyuan, chief engineer at the State Electricity Regulatory Commission, has said that several dams weakened by the earthquake are under 24-hour observation for signs of collapse and may not be able to withstand strong aftershocks or flooding. "The earthquake this time has caused damage at various levels to reservoirs and dams. Safety experts have been put in place to monitor the operation of the dams 24 hours a day."
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