The Dujiangyan Irrigation System is located along the main branch of the Lancang River, west of Dujiangyan City. It was constructed in the Qin dynasty around 256 BC by Li Bing, Prefecture Chief of Shu County, and his son. It is one of the few ancient Chinese water conservancy projects that has remained preserved and intact. The project consists of three primary works—Yuzui Diverting Embankment, the Feishayan Spillway, and the Baopingkou Water Inlet, and two secondary works which include the Baizhangdi (the thousand-feet dam) and Renzidi (the y-shaped dam). They divide the Yongjiang River into an outer and an inner branch, the former of which is used to divert floods and the latter for irrigation. This has allowed the Western Sichuan plateau to become "the land of abundance" as we now know it.