Drainage of the dangerous Tangjiashan "quake lake" in Sichuan Province has gone smoothly since Saturday. However, local government is still on high alert.

Engineering soldiers have fired missiles to blast boulders in a man-made sluice channel to accelerate water drainage.

Xinhua reporters saw at the site the water flow running through the sluice channel has widened from previously less than five meters to about eight meters.

"Generally speaking, construction of the lake's drainage projects goes on well, but the lake remains dangerous for hundreds of thousands of people downstream," said General Ge Zhenfeng, Deputy Chief of the General Staff of the People's Liberation Army (PLA), who is supervising the relief work at the site.

"It will take us a few days to eliminate the potential danger of the lake," said the general.

Some 600 armed police and soldiers worked for six days and nights to dig a 475-meter channel to divert water from the lake.

Xinhua reporters saw that soldiers were still widening and deepening the sluice channel with the help of some 30 bulldozers and excavators. They were also digging a second sluice channel on another side of the lake barrier.

The soldiers have finished building one third of the new channel, which needs to remove about 60,000 cubic meters of earth and stone, said Liu Yongjian, a PLA officer in charge of the channel projects.

"We have also prepared for underwater explosion to deepen the channels for accelerated drainage," said Liu.

The lake started to drain on Saturday morning and water flowed at a speed of more than 10 cubic meters per second, far more than the previous two cubic meters per second, according to the quake lake relief headquarters in Mianyang City.

The water level in the lake stood at 741.70 meters above the sea level at 9 a.m. on Sunday, still 1.33 meters higher than that allowing drainage, according to the headquarters.

Rao Xiping, head of the Beichuan hydrometeorological station, told Xinhua the lake dam remained safe as the drainage went on.

"We found no obvious expansion of the sluice holes nor cracks on the dam. There is no sign of dam collapse either," said Rao, adding the staff of his station and soldiers are keeping 24-hour patrol along the dam.

Water Resources Minister Chen Lei warned that increasing rainfall, aftershocks, landslides and leakage were still threatening the lake's barrier.

The rainfall of 400 mm or 500 mm, well above the normal level, was forecast upstream in June and July, posing a challenge for the swollen lake, he told Xinhua.

Landslides could take place on mountains not far from the lake, which might pour another 17 million cubic meters of rocks and earth into the lake. If it happens, the lake's barrier would immediately burst and workers on the barrier could be swept away, he said.

The Tangjiashan "quake lake" was formed after a massive quake-triggered landslide from Tangjiashan Mountain and blocked the Tongkou River, which ran through the Beichuan County, one of the worst-hit areas in the quake.

Holding more than 220 million cubic meters of water, the swollen lake is the largest of more than 30 quake lakes in Sichuan following the May 12 quake, posing a threat to 1.3 million people downstream.

More than 250,000 people in low-lying areas in Mianyang have been relocated under a plan based on the assumption that a third of the lake volume breached its banks.

Two other plans require the relocation of 1.2 million people if half the lake volume is released or 1.3 million if the barrier is fully opened.

(Xinhua News Agency June 8, 2008)