Dujiangyan is an irrigation infrastructure built in 256 BC during the Warring States Period of China by the Kingdom of Qin. It is located in the Min River in Sichuan province, China, near the capital Chengdu.
It is still in use today to irrigate over 5,300 square kilometers of land in the region. The Dujiangyan along with the Zhengguo Canal in Shaanxi Province and the Lingqu Canal in Guangxi Province are known as "The three great hydraulic engineering projects of the Qin Dynasty".
Description about Dujiangyan Irrigation System by UNESCO
The Dujiangyan irrigation system, located in the western portion of the Chengdu flatlands at the junction between the Sichuan basin and the Qinghai-Tibet plateau, is an ecological engineering feat originally constructed around 256 BC. Modified and enlarged during the Tang, Song, Yuan and Ming dynasties, it uses natural topographic and hydrological features to solve problems of diverting water for irrigation, draining sediment, flood control, and flow control without the use of dams.
Today the system comprises two parts: the Weir Works, located at an altitude of 726m, the highest point of the Chengdu plain 1km from Dujiangyan City, and the irrigated area. Three key components of the Weir Works control the water from the upper valley of the Minjiang River: the Yuzui Bypass Dike, the Feishayan Floodgate, and the Baopingkou Diversion Passage.
Together with ancillary embankments and watercourses including the Baizhang Dike, the Erwang Temple Watercourse and the V-Shaped Dike, these structures ensure a regular supply of water to the Chengdu plains. The system has produced comprehensive benefits in flood control, irrigation, water transport and general water consumption. Begun over 2,250 years ago, it now irrigates 668,700 hectares of farmland.
Li Bing's Irrigation System consists of three main constructions that work in harmony with one another to ensure against flooding and keep the fields well supplied with water: The Yuzui or Fish Mouth Levee, named for its conical head that is said to resemble the mouth of a fish, is the key part of Li Bing's construction. It is an artificial levee that divides the water into inner and outer streams.