The long-awaited drainage of China's Tangjiashan "quake lake" began at 7:08 a.m. Saturday, when its water flowed into a man-made sluice channel.

The flow was rapid, steady and gradually increasing in volume. Liu Ning, the chief engineer from the Ministry of Water Resources, explained the role of the sluice channel.

"Although the volume of flow is not large now, the Jian River which was blocked almost a month ago has been reconnected. This also indicates the water from the upper reaches will not be stored in the barrier lake."

The engineer added that he expected the rapid flow of water would eventually erode the barriers.

"Now we are not merely monitoring the lake. A potential flood could play an important role. We will take some mechanical measures to increase the eroding effect of the flowing water. As a result, the barriers will be removed and water from the upper reaches can flow downstream naturally."

The swollen lake was formed by a massive landslide following the May 12 earthquake that jolted the country's southwest. It held more than 220 million cubic meters of water and posed a threat to about 1.3 million people downstream.