Gao Jianguo, a researcher with the China Earthquake Administration's Institute of Geology, said it was extremely urgent to monitor the newly formed lakes that could burst their banks and cause flooding downstream.

"As the rainy season is approaching, these unstable lakes, or natural reservoirs, pose a serious threat to densely populated downstream areas," Gao said.

In 1933, three newly formed lakes burst their banks 45 days after an earthquake measuring 7.5 on the Richter scale struck Diexi in western Sichuan, he said.

Floods extended 250 km to Dujiangyan, killing 2,500 people.

Chai Hejun, a researcher with the Chongqing Institute of Transportation Design, said 21 percent of the new lakes could breach within a day, 48 percent within 10 days and 88 percent within a year.

Gu Junyuan, chief engineer with the State Electricity Regulatory Commission, said on Monday that all of the hydropower stations along the upper reaches of the Minjiang River, a major river running through the quake-hit areas, were "quite safe".

The hardest-hit area, which has 29 dams, is located in a valley in the upper reaches of the river, he said.

Most of the dams are solid gravity dams or gate dams, which are strong enough to sustain overflowing water.

Five hydropower stations where the earthquake's epicenter was located are relatively small, with a total storage of 1.5 million cu m.

"Even if there are some problems with these dams, we have the giant Zipingpu Reservoir downstream of the Minjiang River," Gu said.

"With a storage capacity of 1.1 billion cu m, it has the capacity to contain the runoff from some of the damaged dams."

The Zipingpu Reservoir is now operating properly after sustaining some minor damage during the earthquake, Gu said.

Firefighters from Tianjin check for cracks on Monday at the Harvest Reservoir in Anxian county, Sichuan.

(China Daily May 21, 2008)