By Xinhua,
Mianyang (China) : China Thursday issued a flood warning as water pressure in the Tangjiashan “quake lake” was building rapidly, aggravating the danger that it could burst its banks.
Emergency teams were hoping to drain the lake but new landslides and higher than expected rainfall have added to the risk of flooding downstream, officials said.
The mud and rock dam, caused by landslide on the Jianjiang river in the May 12 quake, was also in the danger of collapsing under the pressure of increasing water.
More than 600 police and soldiers dug a 475-metre channel to divert water from the lake in Beichuan county of Mianyang city.
The water level at Tangjiashan lake had risen to 738.5 meters by Thursday, still 1.5 metre below the channel.
It is expected that the lake, which holds more than 200 million cubic metres of water, would start draining as soon as the water level reached the lowest point of the dam.
But one official warned late Wednesday the lake could burst its banks in the event of frequent aftershocks, rain on the upper reaches and the instability of the mud and rock dam.
“Water has been seeping out of the dam body,” he said.
“We must prepare for dealing with the worst scenario, but strive for the best results,” Chen Lei, the minister of water resources, said Wednesday.
A massive landslide could occur any time on the upper reaches, which would bring down about 20 million cubic metres of mud and rock into the lake, giving rise to huge waves.
He said draining the rapidly accumulating water in the artificial lake was necessary to “ensure the safety of people downstream”.
More than 250,000 people in Mianyang have been relocated as a precaution.
The May 12 quake triggered massive landslides in southwestern Sichuan province, blocking the flow of rivers and creating more than 30 unstable “quake-formed lakes” that threaten millions downstream.
The 8.0-magnitude quake, centred in Wenchuan county, has left more than 70,000 people dead, about 18,000 missing and millions homeless. More than 10,000 aftershocks have been reported since May 12.