The permanent ship lock of the Three Gorges Water Control Project on the Yangtze River drew public attention Monday morning as trial navigation got underway on schedule.

A passenger ship sails into the fourth chamber of the permanent ship lock as a gate opens at the Three Gorges Dam in Yichang, Hubei Province, June 16, 2003. [Xinhua]

The two-way five-step lock, the largest in the world, was built entirely by Chinese engineers after solving a number of unprecedented technical difficulties.

The lock, completed after about a decade of work at a cost of 6.2 billion yuan (US$746.99 million), features a two-way lifting facility for the 113-meter drop between the upstream and downstream separated by the gigantic dam.

With the lock in operation, ships will be able to pass through the dam in about two and a half hours via the 6.44-km-long dock on the northern bank of the Yangtze River.

The lock has 24 lock gates, each weighing 867 tons, which were built by China's two flagship ship yards located respectively in Wuhan, the capital city of central China's Hubei Province, and in Shanghai, east China.

Previous trial operations and tests have shown that the gates and related opening and closing mechanisms meet sophisticated international standards.

The metallic structures and electronic equipment of the lock gates were manufactured and installed by 16 large Chinese enterprises from 14 provinces and municipalities.

Scheduled for completion in 2009, the Three Gorges Project will start to pay dividends this year, playing an important role in flood control, power generation, navigation, water diversion and environmental protection.