A senior official said here on Tuesday that a "decisive victory" have been achieved in the drainage of China's main quake lake Tangjiashan.
Liu Qibao, Communist Party chief of the southwestern Sichuan Province, made the remarks after about half of the quake's water have been discharged and the number of people under threat has dropped from 1.3 million to less than 50,000.
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, according to the Tangjiashan Lake emergency rescue headquarters.
The lake's dam was also more secure with the sluice channel being lowered, the headquarters said.
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 water level in the lake reached 720.25 meters above sea level as of 7 p.m. Tuesday and the lake's volume was 110 million cubic meters as the daily average influx reached 454 cubic meters per second.
For the 352 villagers in Qinglian town, Jiangyou city, who had left home and lived in tents for more than ten days, the turbid water was good news for them.
When the flood water approached the town on Tuesday morning, the villagers all went out of their tents and headed to places most close to the flood, watching the flood going south.
"After the flood goes away and the government disinfects the town, I'll go back to my factory. I hope it could restore production soon," said Zhou Yumin, a local resident and clothing manufacturing company employee, happy to see the flood going away.
In another settlement in Fucheng District, Mianyang city, several aged people in their 70s and 80s were watching TV in their temporary mobile house when the flood water passed by.
"When the flood is over, I could go home to plant my crops," said Song Tianming, 79.
The 250,000 people who were evacuated would be able to go back home in two or three days as the overflow continued, said Water Resources Minister Chen Lei at 5 p.m..
"The best situation is to completely clear out the water in the Tangjiashan lake before the flood season. The water level is likely to linger around 720 meters for a period of time," he said . "We'll take advantage of the time to eliminate the risk as soon as possible," he added.
Experts provided three schemes to eliminate the risk. One was to use engineering techniques, including blasting, to lower the sluice height to 710 m. The second was to reinforce the dam during the flood season. The third was to restructure the quake lake into a reservoir.
All three schemes had to be evaluated after the water flows were going steadily and a thorough geologic observation had been carried out on the dam, they said.
The man-made spillway started to drain from the lake on Saturday morning and military engineers used recoil-less guns, bazookas and dynamite 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.
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 quake relief headquarters of the State Council (cabinet) Tuesday sent a congratulatory telegram to the Tangjiashan lake emergency rescue headquarters for the successful drainage of the quake lake.
"After more than 10 consecutive days of hard work, you successfully drained the Tangjiashan quake lake and eliminated a huge threat of secondary disaster after the May 12 quake," the telegram said.
"Your work has ensured the people's security, avoided a huge loss and created a miracle in dealing with large quake-formed lakes," it said.
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.
(Xinhua News Agency June 10, 2008)