The Dujiangyan irrigation system on the Min river is one of the oldest irrigation systems still in operation. The project began in 256 BC when Li Bing and his son, Er Lang, diverted the river into a man-made channel and constructed a system to control flooding and remove silt. It was put on the World Heritage List in 2000.
Dujiangyan has three major parts:
The river is split into two parts as it enters the Fishmouth pier, a long and narrow dike built in the shape of a fish mouth in order to receive the least water resistance. The Feishayan weir drains the flood water and takes away sediment deposits. 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. On average, 40 percent of river's runoff goes into the inner river in flood season, 60 percent into the outer, and vice versa in the dry season. The inner river diverts water into Chengdu Plain through Baopingkou, and the outer river is the main flow, which carries off 80 percent of the silt.
The Anlan bridge is suspended by woven bamboo cables. It was formerly called the Fuqi Bridge (Husband and Wife Bridge) because it was built by a devoted couple and it is held together by locks that symbolize the pair's never-ending devotion.
There is a large park area around Dujiangyan with various temples and pavilions sprinkled through the forest and gardens. Erwang Temple (two kings temple) was built as a tribute to Li Bing and his son. The oldest tree in China dating back to the Yin Shang dynasty (1700-1100 BC) is also in the park.
A bird's-eye-view of the whole system can be found by climbing up the five-story high Qin Yen Lou. Mao, Deng, and Jiang Zemin have all taken in the view from its upper platform.