Construction of the Dujiangyan irrigation project was begun by Li Bing, king of west Sichuan, in 256 B.C. and completed by his son, Er Lang. When Han settlers first arrived 2,200 years ago, the area was a flat plain plagued by frequent summer floods (and winter droughts) caused by the Minjiang, a Changjiang tributary that flows through the Chengdu/Chuan Xi plains. Workers using only hand tools cut a trunk canal, called the "Mouth of the Precious Jar," through a towering mountain in order to feed an extensive system of canals on the plains, thereby turning the Chengdu plains into one of the most fertile in China and giving rise to the description of Chengdu as Heaven on Earth.

The project has been maintained and expanded ever since, and it is perhaps one of the world's oldest irrigation schemes in continuous use today. The Sichuanese are very grateful to Li Bing and his son. Both men have been deified (with temples built for them at Dujiangyan and elsewhere), and ceremonies are held every year to commemorate their achievements.