The Three Gorges Dam is a hydroelectric gravity dam that spans the Yangtze River by the town of Sandouping, in Yiling District, Yichang, Hubei province, central China, downstream of the Three Gorges. The Three Gorges Dam has been the world’s largest power station in terms of installed capacity (22,500 MW) since 2012.

The dam body was completed in 2006. The power plant of the dam project was completed and fully functional as of July 4, 2012. The last major component of the project, the ship lift, was completed in December 2015.

A boat lift, ship lift, or lift lock is a machine for transporting boats between water at two different elevations, and is an alternative to the canal lock.

In addition to the canal locks, there is a ship lift, a kind of elevator for vessels. The ship lift can lift ships of up to 3,000 tons. The vertical distance traveled is 113 m, and the size of the ship lift’s basin is 120 m × 18 m × 3.5 m. The ship lift takes 30 to 40 minutes to transit, as opposed to the three to four hours for stepping through the locks. One complicating factor is that the water level can vary dramatically. The ship lift must work even if water levels vary by 12 m on the lower side, and 30 m on the upper side.

The system works using a fixed rack of gear teeth stretching the full height of the lift. The basin containing the ships and the water they float in then travels up and down this rack using a helical worm gear. Each traversal takes about 40 minutes.

According to Wikipedia