Dujiangyan is not only an ancient engineering project, but also an experiment on "how humans can coexist with nature." For over two thousand years, from the Warring States period to the present, it has quietly operated, continuously supplying the Chengdu Plain with vital water. Rather than a water conservancy facility, it is more of a design philosophy: using the terrain as a brush and water as ink, making nature an integral part of the system.
Engineering wisdom that follows the trend
When Li Bing and his son designed the Dujiangyan Irrigation System, they did not choose to use a high dam to forcibly divert water. The technology at that time was actually sufficient, but they did not do that.
Their decision was "not to confront," but to "guide": to let the water flow according to the mountain's contours and the terrain, completing its own diversion, sediment removal, and irrigation.
This reflects an Eastern way of thinking: the stability of a system comes from balance, not control.
Modern people talk about "sustainable design," but Li Bing was already practicing it two thousand years ago. Without concrete or steel bars, yet able to self-regulate by relying on terrain and water flow, this engineering logic is more complex and intelligent than "building dams."
Of course, this ancient wisdom is not universally applicable. The climate was relatively stable back then, and there were no surface hardening problems caused by modern urbanization. To directly apply the Dujiangyan concept to contemporary cities, it must be redesigned and rebalanced.
The triple mechanism of water diversion, sediment removal, and water introduction
The essence of Dujiangyan lies in its three core structures.
Fish Mouth: A Natural Water Dividing Hub
The Fish Mouth Dam, built at the bend of the Minjiang River, divides the river into two parts: the inner river and the outer river.
During the dry season, the water flow is slow, and more water flows into the inner river for irrigation; during the wet season, the outer river automatically shares the flood discharge burden.
The entire process is gateless, relying entirely on the natural regulation of terrain elevation and flow rate. This design itself is an "automatic logic".
Feisha Weir: Letting the silt and sand leave on their own
Silt is the biggest enemy of rivers. Li Bing designed the Feisha Weir, which has a low weir body. When the water volume rises and the flow velocity increases, silt and rocks will be discharged into the outer river with the flood.
This mechanism eliminates the need for frequent dredging and ensures the smooth flow of water diversion channels.
In other words, the Feisha Weir makes "maintenance" a part of the natural cycle.
Bottle Neck: The Lifeline to the Plains
The Baopingkou (Bottle Neck) acts like a bottleneck, controlling the flow of water in the Neijiang River.
Its curved design allows water to flow smoothly into the Chengdu Plain without causing erosion.
This small water intake may seem simple, but it actually reflects an extremely high level of understanding of hydrology and topography.
These three parts form a dynamic balance system: water diversion, sediment discharge, and water diversion. They restrict and support each other, which constitutes the secret to the long-term operation of Dujiangyan.
The ingenuity of technology and modern questions
The most amazing thing about Dujiangyan is that it can be controlled without being controlled.
The ratio of water distribution at the fish mouth changes naturally between 4:6 and 6:4 depending on the season and water level.
This is not a miracle, but a perfect application of fluid mechanics. In an era without computers and models, the ancients constructed natural algorithms based on experience and observation.
But problems arise: this mechanism relies on natural stability, but climate change is making floods more violent and sand sources more unpredictable.
While modern engineers reinforce structures with concrete, they cannot fully replicate that "adaptive" flexibility.
So, can Dujiangyan serve as a template for contemporary water conservancy design? Perhaps, but it must be reinterpreted.
Inspiration for modern cities
Nature-oriented design thinking
Modern urban water systems often rely on closed structures: reservoirs, pumping stations, and drainage networks. Dujiangyan offers an alternative approach—making natural forces an integral part of the system.
The concepts of "green infrastructure" or "resilient city" are actually aligned with the ideas of Dujiangyan: reduce intervention and increase self-regulation.
The Logic of Sustainable Operation
According to research ("Sustainability of the Dujiangyan Irrigation System", ResearchGateThe Dujiangyan Irrigation System has been able to operate continuously for two thousand years because it has achieved a stable balance between flood control, irrigation, and ecology.
This diversion mechanism allows the system to automatically switch functions in different seasons without manual intervention. This low-intervention, high-flexibility approach is precisely the core of contemporary sustainable engineering.
The reintegration of urbanization and ecology
Recent studies(MDPI, Land, 2022)Using the Dujiangyan Irrigation District as a case study, this paper explores the ecological connectivity between farmland, waterways, and the urban fringe.
When the irrigation system is integrated with recreational and landscaped spaces, it can still maintain its original water conservancy function.
This reminds us that urban waterways are not just functional facilities, but also part of an ecological network.
New Issues in Water Rights and Governance
The expansion of modern Chengdu has brought about new contradictions.
Water resources are no longer just an agricultural issue; they also involve urban drinking water, water rights allocation, and protected area management.(Tandfonline, 2023).
This made us realize that design is not a one-time outcome, but a dynamic and coordinated process.
If Dujiangyan were built today, its mission would be more than just water diversion; it would also be about responding to the complex relationship between ecology and society.
From Ancient Methods to Future Design
The value of Dujiangyan lies not only in the technology itself, but also in the way of thinking behind it.
It represents a design attitude of continuous dialogue: understanding nature, observing change, and allowing flow.
If future cities can learn from this logic, they may no longer need to rely on massive artificial flood control systems, but can instead coexist with nature through a more sophisticated network.
In the history of engineering, many great designs have succumbed to the passage of time, but Dujiangyan has triumphed for two thousand years. Perhaps this is the highest realm of design: not to make nature submit to man, but to teach man to work in harmony with nature.
