China's main quake-formed lake at Tangjiashan in the southwestern Sichuan Province shrank drastically on Tuesday as muddy water flows into the low-lying areas.
About half of the lake's 250 million cubic meters of water has been discharged since the drainage started on Saturday morning, the Tangjiashan lake emergency rescue headquarters said.
Sichuan Communist Party chief Liu Qibao said Tuesday afternoon that a "decisive victory" has been achieved in the drainage of the quake lake.
Picture taken on June 10, 2008 from a military helicopter shows flood water flowing past Beichuan County in southewest China's Sichuan Province. Drainage of the Tangjiashan quake lake through a manmade spillway speeded up to 1,760 cubic meters per second at 9:30 am on Tuesday, whereas water flow in the lower reaches of the lake, in Beichuan County, reached 2,240 cubic meters per second. A man-made sluice channel on the lake's dam was scoured to between 720 and 721 meters above the sea level at 5 p.m., which means the influx and outflow of the lake reached a balance, experts with the headquarters said.
Drainage of the quake lake through the spillway speeded up to 6,420 cubic meters per second at 11:30 a.m., before it slowed to a steady 3,888 cubic meters per second at 2:30 p.m..
The crest of the flood from the lake on Tuesday afternoon passed safely by downstream Mianyang City, where between 300,000 and 400,000 people were left, said Tan Li, the city's Communist Party chief and also its Quake Control and Relief Headquarters head.
More than 250,000 people in low-lying areas of Mianyang had been relocated under a plan based on the assumption that one-third of the lake volume breached the dam.
A few villages and farms in Jiangyou City, a city sandwiched between Beichuan and Mianyang, were flooded, but seven towns along the river were not, said the city's Communist Party chief Yi Lin. There were no reports of casualties.
Xinhua reporters in Jiangyou saw trees, barrels, TVs, fridges and the occasional dead bodies of quake victims in the roaring flood water.
Great noise was heard at Tongkou Town along the Tongkou River, where the water level surged by about 20 meters from Monday.
Due to the torrential outflow, the lake water level kept on decreasing from 740.37 meters above the sea level when the spillway became operational on Saturday morning.
The brownish lake water burst the dams of four smaller quake lakes on the lower reaches of Tangjiashan and flowed into the low-lying Beichuan County that had been flattened in the 8.0-magnitude quake on May 12.
Faster drainage of the Tangjiashan Lake had eased the peril on the lower reaches, but the emergency headquarters was still on alert for further landslides and dam bursts, said Commander-In-Chief Jiang Jufeng.
Hydrological workers had already observed cracks in the dam, and helicopters were arranged to evacuate all the emergency workers, mostly soldiers with the People's Liberation Army (PLA) and the armed police.
More than 200 armed police officers worked round the clock for four days to drain the lake. Once overflowed, it could threaten some 1 million residents living on the lower reaches.
A man-made spillway started to drain from the lake on Saturday morning and military engineers used recoilless guns, bazookas and dynamites on Sunday and Monday to blast boulders and other obstructions in the channel and speed up the outflow.
As a result of two massive blasts on Monday evening which broke through the "bottleneck" in the spillway, the water outflow speeded up drastically on Tuesday compared with 80 cubic meters on Monday night.
The Tangjiashan quake lake, formed after quake-triggered landslides from the Tangjiashan Mountain, blocked the Tongkou River running through Beichuan County, one of the worst-hit areas in the May 12 quake.
Source:Xinhua
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