(Xinhua)
Updated: 2008-05-31 09:01

MIANYANG -- Up to 1.3 million people in southwest China's Sichuan Province have been ordered to evacuate to higher grounds for fear of a major "quake lake" burst as a result of flooding and strong aftershocks.

Residents start evacuating from downtown Mianyang, Sichuan province, on Friday as the threat of a quake lake bursting its banks mounts. [Xinhua]

Tan Li, Party Secretary of Mianyang City and chief of Mianyang City Quake Control and Relief Headquarters, on Friday renewed an order that 1.3 million people living downstream from Tangjiashan, a swelling quake-induced lake, must evacuate to higher grounds demarcated by government departments.

Tan's renewal of the order -- the issue of the No. 1 order -- within less than a day is considered as a contingency plan to guarantee zero deaths in the resident evacuation in case the Tangjiashan Lake barrier collapses completely.

At 4 pm on Thursday, Tan issued a No. 1 order demanding about 200,000 people living downstream from Tangjiashan in the main urban districts of Mianyang City should start evacuation by 8 am on Saturday. The evacuation must be completed by 8 am on Sunday.

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

An aerial view shows an SOS sign made in a farmer’s field at avillageofBeichuancounty, May 28, 2008. Heavy rains increased the water level of the Tangjiashan quake lake, formed when a landslide triggered by the May 12 quake blocked the Jianjiang River. [Xinhua]

As of 6:30 pm on Friday, 174,708 people had been moved from Mianyang with nearly half being evacuated on Friday alone.

More than 40,000 cubic meters of debris was removed on Friday, driving up the total to more than 110,000 cubic meters.

The mass evacuation, dubbed a "drill" by local government officials, is said to make way for a possible flood discharging operation set for the weekend.

The evacuees, who were told to carry supplies for one week's survival, were arranged to stay inside government-financed temporary accommodation shelters erected on safe grounds -- open areas in forested land or hilly slopes -- not far away from their original residences.

In accordance with a notice posted by the Tongkou Township government of Mianyang City seen by Xinhua reporters at the site, starting at 8 a.m. on Saturday till the warning is lifted, all people are banned from activities at a line below 36 meters -- a mark the level of the flood water might come up to when the quake lake fully opens.

The seat of Tongkou, about 30 kilometers away from Tangjiashan Lake, seemed like a deserted place: gone were the old, weak, sickened and disabled, only a number of young people were seen collecting and moving valuable property.

Zhou Congcai, chief of the Tongkou government, told Xinhua reporters all 708 households in his township, with 1,853 individuals involved, should have evacuated to safe grounds together with their property by 8 pm on Friday.

"If Tangjiashan Lake fully opens, the water level could come up to 36 meters at Tongkou Township, and the township government headquarters will be submerged," said Zhou. "All the masses of the people are evacuated to higher places 40 meters away from the bed of the river course. The move to take the worst situation into consideration to guarantee zero deaths during evacuation."

Local police and militia will sort out and take over the management of the evacuated zones to make sure no one is left behind. The evacuated zone will be sealed off from visits.

The effort to prevent Tangjiashan Lake from bursting has topped the country's relief work agenda.

In a phone call on Monday night, Chinese President Hu Jintao told Vice Premier Hui Liangyu, who was in Sichuan to oversee the quake-relief work, that the relief task force must make sure no serious problems occur in the emergencies.

"We must put people first and the priority is to protect their lives," Hu said.

Premier Wen Jiabao said in Beijing on Tuesday the relief headquarters will evacuate residents from the area downstream of the lake and at the same time, try to drain the water. "We must well prepare and do the two parts of work side by side."

The unprecedented attention to the swelling quake lake is not without reason.

An earthquake measuring 7.5 magnitude hit Diexi in Maoxian, close to Wenchuan, the epicenter of the 8.0-magnitude quake on May 12, in 1933,leading to the formation of 11 quake lakes. According to historical records, more than 500 peopled were killed in the quake, but the collapses of quake lakes two months later that year claimed the lives of 20,000 more.

The fear that Tangjiashan Lake, formed by landslides that blocked a river known as the Jianjiang after the May 12 quake, might be at risk of breaching its bank has worsened as heavy downpours started about 10 p.m. on Wednesday and lasted into Thursday around Tangjiashan, driving up the water level in the lake.

Tangjiashan, one of 35 such lakes, is inaccessible by road and can only be reached by foot or air.

By 4 p.m. on Thursday, the water level was 745.5 meters at its highest point before the debris blockage, about 22.78 meters from the lowest barrier.

Meanwhile, rescuers had completed construction of a sluice -- a irregular cube designed to discharge flooded water -- from Tangjiashan quake through painstaking efforts in the past five days.

The sluice, measuring 300 meters in length and 50 meters in width, was dug nine meters upstream and 13 meters downstream.

The bottom of the sluice is still 9.6 meters above the water level in the quake lake, according to Yue Xi, deputy chief of the armed police hydropower detachment.

"The volume of water in Tangjiashan Lake has increased rapidly due to rainfall in the past days. It will take days before the water level in the quake lake can meet the bottom of the sluice. The moment when water in the quake lake flows downstream through the manmade water diversion facility won't happen before June 4," said Yue.

The death toll from China's earthquake on May 12 increased by about 340 overnight to 68,858 as of Friday noon, the Information Office of the State Council said. Another 366,586 people were counted as injured and 18,618 were still listed as missing.

The seismological observatory in Sichuan Province is predicting that more aftershocks will continue along the northern end of the Wenchuan-Beichuan-Qingchuan faultline in the coming days, with the most powerful being estimated to go around 6.5 in terms of magnitude.

According to the observatory, the above-mentioned faultline and its adjacent areas suffered 8,911 aftershocks by midday on Wednesday.