Đê chia nước "Miệng cá" khu Đô Giang Yển

Yuzui, the "Fish Mouth" water-dividing dike, is one of the three great engineering works of the Dujiangyan Irrigation System and the piece that gives the entire site its function. Standing in the middle of the Min River at the upstream edge of the Irrigation System, it is the structure that first meets the river as it flows down from the mountains, and the structure that sets the entire hydraulic logic of the site in motion. For visitors walking through the UNESCO World Heritage area, it is one of the most dramatic and most-photographed points along the route.

The role of Yuzui is to divide the Min River into two channels: an outer river, which carries the bulk of floodwater away downstream, and an inner river, which feeds the irrigation network that has watered the Chengdu plain for more than two thousand years. The dike is shaped like the elongated, pointed head of a fish, from which it takes its name, with the pointed end facing upstream into the current. The geometry of the divide is not equal; in the dry season, roughly six tenths of the water is directed into the inner river for irrigation, while in the flood season the proportions shift and a majority of the water and silt is carried away by the outer river, all without any moving parts or external power.

Standing on the dike, it is possible to see the river split in real time, the water visibly parting around the pointed tip of the structure into two channels that run off in different directions. The site is reached on foot as part of the walking circuit through the Irrigation System, usually crossed by way of the Anlan Suspension Bridge, which sways above the river between the two banks. The dike itself is built up from local stone and traditional bamboo cribbing, in keeping with the construction methods that have been used and rebuilt across the centuries.

Yuzui is best understood as part of the larger Dujiangyan works rather than in isolation, and it appears in every guided explanation of the Irrigation System. It is most impressive in the summer flood season, when the river runs heavy and the dividing work of the dike is most visible, and in the early morning, before the tour groups arrive and while the river is still in good light.