Not many engineering feats can rival China’s Grand Canal. Stretching over 1,770 kilometers from Hangzhou to Beijing, this waterway shockingly holds the title for both the world’s oldest and the world’s longest canal. For much of its 2,500-year history it was China’s central economic artery, helping to unify the vast country. It was here that the pound lock was pioneered.
The earliest segments of the canal were constructed around 500 BCE. At the time, China was fragmented into numerous states, many of which built their own canals for domestic and military purposes. The potential of connecting these disjointed segments was first realized by the Sui Dynasty in the 6th and 7th centuries CE. In a vast effort involving millions of workers, the government joined the many canals into a new mega-canal between Beijing and Hangzhou, adding hundreds of miles of navigable inland waterways.
The canal’s central purpose was to transport grain from China’s agricultural centers in the south to its economic and political centers in the north, above all the thriving capital of Beijing. This new infrastructure enabled additional urban growth, extended the government’s administrative control, and provided a quick and effective method of communicating over large distances.
Among various improvements made over the years to increase the canal’s efficiency and navigability, the most notable was the invention of the pound lock in the 10th century by Qiao Weiyue, a skilled Chinese engineer and bureaucrat. This now-common invention allowed ships to safely ascend or descend through rapid changes in level. It consists of a series of gated chambers or “steps” in which the water level is gradually raised or lowered, lifting ships up or down the incline. This ingenious device continues to be in heavy use over 1,000 years later, as a feature in almost every modern canal or river that has differing water levels.
Today, only a small southern section of the canal is navigable by modern commercial vessels. But the rest of the canal is not lying dormant. It is proving its importance yet again as a part of China’s massive South-to-North Water Diversion Project, bringing fresh water to thirsty Beijing.
It is rare that a project that has stood for millennia can remain a relevant and record-breaking site, which is why China’s Grand Canal is regarded by many as one of mankind’s greatest accomplishments of hydraulic engineering.