Britannica Sources used in this answer

How did early Chinese canal gates control water levels?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

View of Utrecht's Oude Gracht canal lined with historic brick buildings, arched doorways at water level, and boats moored along the canal edge in the Netherlands. — canals and inland waterways The *Oudegracht* (Old Canal), Utrecht, Netherlands.

Early Chinese canal systems managed water levels using several methods depending on the terrain and the scale of the waterway.

At approximately 5-kilometer (3-mile) intervals, canals were equipped with single gates featuring stone or timber abutments. These gates included vertical grooves along which a log closure was manually hauled by ropes to either hold back or release water, thereby controlling the water level. For more complex requirements, some gates were designed to be raised using windlasses.1

In instances where the changes in water level were too significant for these simpler devices, engineers constructed double slipways, which allowed vessels to be hauled up or down the inclines. By the 9th century, the Ling Canal was rebuilt with a system of locks, which were later improved in the 11th or 12th century with a series of 36 locks to accommodate larger vessels.12