Dujiangyan

The Dujiangyan is an ancient hydraulic engineering system in Dujiangyan City, Sichuan, China, on the Min River, one of the longest tributaries of the Yangtze, in the west of the Chengdu Plain. The State of Qin built it around 256 BC as an irrigation and flood control project, and it is still in use today. Before it existed the Min rushed down from the mountains and slowed abruptly on the plain, silting up the watercourse and causing floods. The Qin hydrologist Li Bing chose not to dam the river, because the Qin wanted the waterway kept open for military vessels, and built an artificial levee that divides the flow, then cut a channel through Mount Yulei to carry the excess water away. The scheme has three main parts, the Yuzui or Fish Mouth Levee, the Flying Sand Weir and the Bottle-Neck Channel, which work together to control floods and silt. It now irrigates more than 5,300 square kilometers of land. The original system was destroyed by the 1933 Diexi earthquake and rebuilt afterward. Dujiangyan was inscribed on the World Heritage List in 2000, and it is known with the Zhengguo Canal and the Lingqu Canal as one of the three great hydraulic engineering projects of the Qin.