The Gezhouba Dam (Gezhouba Water Control Project, Chinese: 长江葛洲坝水利枢纽工程) is an afterbay (smaller dam in front) of the Three Gorges Dam. It forms a pool that extends upstream to the base of the Three Gorges Dam, improving navigation. The dam was built from December 30, 1970 to December 10, 1988. The dam is long and up to tall. It generates 2,710 megawatts of electricity. There are three ship locks at the dam. Lock No.2, which is long, wide, and deep, is among the 100 largest in the world.