By Zhang Haizhou (China Daily)
Updated: 2008-05-24 09:11

The largest "barrier lake" formed by the earthquake in Sichuan should not pose an immediate danger to Tangjiashan residents as they evacuate the village, Zhu Bing, deputy director of the provincial water resources bureau, said on Friday.

Landslides that blocked rivers in the province have formed 34 barrier lakes, or "quake lakes", the largest of which is about 3 km northwest of Beichuan county in Tangjiashan.

"The data and statistics we have suggest there won't be a complete collapse of the lake's banks in the near future," Zhu told a briefing in Beijing, adding a total collapse, which would cause serious flooding, was possible in the long run.

"After all, it's in an area where there have been aftershocks, and a strong aftershock or thunderstorm could destroy the lake's banks."

Tangjiashan Barrier Lake is considered the most dangerous quake lake because it contains the most water.

As of Wednesday, it contained nearly 100 million cu m but has a 220 billion-cu-m capacity. To date, only eight of the quake lakes had filled up with more than 3 million cu m of water.

According to the Xinhua News Agency, a collapse of Tangjiashan Lake's banks would affect up to 70,000 people living near the lower reaches of the Qianjiang River, along which the lake is located.

"We'll continue with engineering efforts at the lake site and with the evacuation of residents near the river's lower reaches," Zhu said.

But the evacuation has proven tricky, because the lake's water level has been rising rapidly, reaching 716 m on Wednesday compared to 711 m the day before.

A group of hydrological experts who inspected the lake on Wednesday set 751 m as the danger mark.

The Shanghai-based China Business News quoted one of them as saying the continuous rainfall had been the primary cause of the water level's rise.

The experts also estimated that at the current rate, the lake's banks would burst and flood the river's lower reaches in about 20 days.

The city of Jiangyou is at the greatest risk of being flooded, while Mianyang and two counties to the east - Shantai and Shehong - would also be affected, the experts said.

Tang Debin, deputy director of the Jiangyou water resources bureau, said residents of the city are being evacuated.

"We'll evacuate all residents threatened by the lake's bursting before May 24 (Saturday)," Tang said, adding that more than 28,000 people remained in danger.

"We'll move them to higher places or out of the area at risk of flooding."

More than 20,000 residents from 6 townships were expected to withdraw to safe places till midnight Friday.