Cao Guangjing, vice general manager of the China Three Gorges Project Corporation, said the cost of transportation from the Three Gorges to the Chongqing Municipality 664 kilometers away could be reduced by 40 percent.

Jin Yihua, director of the Yangtze River Administration of Navigational Affairs, estimated the annual shipping capacity of the ship lock would rise to 100 million tons.

Before the water level was raised in 2003, a submerged reef hindered night navigation in the Three Gorges area and annual shipping capacity was about 10 million tons.

The capacity in 2006, however, topped 50.24 million tons.

"The Yangtze River has surpassed the Mississippi and the Rhine to become the world’s busiest navigable river," said Jin.

The largest of its kind in the world, the lock has been restricted to one-way traffic, alternating every 24 hours, since last September when work began to raise the beds of the two uppermost tiers.

Traffic on the southern track resumed in January.