The Dujiangyan (Chinese: 都江堰; pinyin: Dūjiāngyàn) is an ancient irrigation system in Dujiangyan City, Sichuan, China. Originally constructed around 256 BC by the State of Qin as an irrigation and flood control project, it is still in use today. The system's infrastructure is on the Min River (Minjiang), the longest tributary of the Yangtze. The area is in the west part of the Chengdu Plain, at the confluence between the Sichuan basin and the Tibetan plateau. Originally the Min rushed down from the Min Mountains, but slowed abruptly after reaching the Chengdu Plain, filling the watercourse with silt, which made the nearby areas extremely prone to floods. Li Bing, then governor of Shu for the state of Qin, and his son headed the construction of the Dujiangyan, which harnessed the river using a new method of channeling and dividing the water rather than simply following the old way of dam building. It is still in use today to irrigate over 5,300 square kilometres (2,000 sq mi) of land in the region. The Dujiangyan, the Zhengguo Canal in Shaanxi and the Lingqu Canal in Guangxi are collectively known as the "three great hydraulic engineering projects of the Qin."