Excerpts from Books and Wikipedia
"In 984, during the construction of China's Grand Canal, engineer quao Weiyo noted that in placing two flash locks 750 feet (229 m) apart, he had created an intermediate stretch of water that could be held at the level of either the upper or lower reach of the waterway, and thus the pound lock, or chamber lock, was born." [1001 Inventions, p. 141] "The oldest parts of the canal date back to the 5th century BCE, but the various sections were first connected during the Sui dynasty (581–618 CE). . . . The canal was built by conscripted laborers and connected the Yellow River in the north with the Yangzi River in the south, which made it much easier to transport grain from the south to the centers of political and military power in north China. The total length of the Grand Canal is 1,776 km (1,104 mi). Its greatest height is reached in the mountains of Shandong, at a summit of 42 m (138 ft).[3] Ships in Chinese canals did not have trouble reaching higher elevations after the pound lock was invented in the 10th century, during the Song dynasty (960–1279), by the government official and engineer Qiao Weiyue." [Wikipedia]