This year's second largest flood has crested and safely passed the Three Gorges Dam on the Yangtze, China's longest river, on Tuesday, forcing engineers to close the locks at the dam.

The ship locks have been closed since 8 pmMonday and more than 100 ships have been detained at the site, but all are in good order. The maritime authority is now making efforts to avoid congestion.

The ship locks are supposed to open after water flowing into the reservoir falls to 45,000 cubic meters per second.

Water flowing into the reservoir of the dam reached 56,000 cubic meters per second at 2 p.m., the highest since the flood earlier peaked at 70,000 cubic meters per second on July 20, the Yangtze River Flood Control and Drought Relief Headquarters said in a statement.

The water flow fell to 53,000 cubic meters per second at 8 p.m.

It said the dam took the edge off the fierce flow by holding back about 31,000 cubic meters of flood water per second and discharging the rest.

The water level in the dam was 154.3 meters at 8 pm, an increase of more than 4 meters in 24 hours and well above the 145-meter flood alarm level, the statement said.

It added that the water level was likely to top 160 meters later on Tuesday.

The water flow is expected to fall to 45,000 cubic meters per second on Wednesday and 35,000 cubic meters per second on Thursday.

Before the flow subsided, the Three Gorges Dam would hold back 8 billion cubic meters of water in total, the statement said.

The dam has slowed the flow of about 15 billion cubic meters of water in the previous four flood peaks since mid June, it said.

Torrential rains battered the upper reaches of the Yangtze last week, with rainfall being held in the catch basins of the Minjiang, Tuojiang and Jialing rivers, three Yangtze tributaries.

Due to heavy rains this summer, shipping through the Three Gorges Dam was suspended twice in July when water flow peaked at 56,000 and 48,500 cubic meters per second, respectively.

The Three Gorges Project is a multi-functional water control system built on the upper and middle reaches of the Yangtze. With a 2,309-meter long dam, a five-tier ship lock system and 26 hydropower turbo-generators, its key roles include flood control, power generation, shipping and water supply.

(Xinhua News Agency August 24, 2010)