Another reason the dam was built was for water navigation, or the transport of people and goods by ship. There are two sets of locks each of which has five stages. Each lock is long, wide, and deep, which is similar in size to the original locks of the Panama Canal, one of the biggest canals in the world. The reservoir behind the dam floods dangerous sections of the river, so boats and ships can go safely and easily. There is also a "ship lift" (an elevator for ships) that can lift ships that weigh up to 3,000 tons.