Rescue workers have been using large earth-moving equipment to dig a channel to drain a lake formed by China's huge earthquake this month.

The barrier lake is situated in Beichuan County, Sichuan Province. It is one of dozens caused by the 8.0 magnitude quake, which sent millions of tons of earth and rocks tumbling into some of the region's narrow valleys.

The irrigation channel was designed to release some of the pressure from the lake.

Dai Runquan is an expert from the Yangtze River water committee.

"Now the flow of water is two cubic meters per second, in certain conditions this place can let 20-30 cubic meters of water through per second. This will largely prevent the water from rising in the upper stream, and lower the pressure from the water."

However, pressure is building up as rivers and streams feed into the newly formed barrier lakes. Adding to the threat, thunderstorms were forecast for parts of Sichuan this week.

Another quake lake, the Tangjiashan lake in northern Sichuan province, is also posing a destructive threat in the disaster zone.

In case of emergencies, rescue workers have made plans to evacuate the local residents.

Lin Xin, vice mayor of a local municipality, elaborates on this plan.

"If one third of the bank in Tangjiashan Barrier Lake bursts, we will evacuate 158, 000 residents in 33 towns and villages. If half of the bank bursts, 1,000,000 and 200,000 people will be evacuated. And if all of it bursts, we will have to evacuate 1,000,000 and 300,000 people."

Now the evacuation work is already underway, with over 80, 000 residents having been successfully transferred to safe areas.