The Ultimate Guide to the Dujiangyan Irrigation System

Introduction: The Ancestor of World Water Culture

Located in the west of Dujiangyan City, Sichuan Province, sitting majestically on the Minjiang River, lies a miracle of engineering that defies time. This is the Dujiangyan Irrigation System, a UNESCO World Heritage site and the only surviving non-dam irrigation system in the world that is still in use today,.

Built over 2,200 years ago around 256 BC during the Warring States Period, this project transformed the Chengdu Plain from a region plagued by perpetual floods and droughts into the "Land of Abundance" (Tianfu),. Unlike modern dams that block water, Dujiangyan works with the water, utilizing natural topography and fluid dynamics to manage the flow. It stands as a testament to the wisdom of the ancients, embodying the philosophy of harmony between humanity and nature. For any traveler visiting Chengdu, a pilgrimage to this ancient engineering marvel is mandatory to understand the very foundation of Sichuan's prosperity.

The History: Born from the Flames of War

While we often view Dujiangyan today as a benevolent agricultural project, its origins were rooted in military strategy. In the 3rd century BC, the Qin State conquered the Shu State (modern-day Sichuan). The Qin strategist Sima Cuo proposed a plan to attack the rival Chu State by sailing down the Yangtze River from Sichuan. However, the Minjiang River was unpredictable—turbulent in summer and too shallow in winter—making the transport of troops and supplies impossible.

In 256 BC, Li Bing, the governor of the Shu Prefecture, was tasked with taming this wild river. His mission was to turn the Minjiang into a reliable strategic supply line for the Qin unification wars. He and his son, along with local laborers, undertook this massive challenge. They did not just build a canal; they fundamentally reshaped the geography of the region using fire, water, and bamboo cages, leaving a legacy that has outlasted empires,.

The Engineering Triad: How It Works

The brilliance of Dujiangyan lies in its three main components: the Yuzui (Fish Mouth), the Feishayan (Flying Sand Weir), and the Baopingkou (Bottle-Neck Channel). These three parts work in perfect synchronization to automatically divide water, discharge floods, and remove silt.

1. Yuzui (The Fish Mouth Water-Dividing Dam)

Your journey into the mechanics of the system begins at the Yuzui. As the name suggests, this is a diversion dike shaped like the mouth of a fish. It is built mid-stream to divide the surging Minjiang River into two parts:

• The Outer River (West): This is the main course of the river, used primarily to discharge floodwaters.

• The Inner River (East): This is an artificial channel that leads water toward the Chengdu Plain for irrigation and daily use.

The Yuzui utilizes a brilliant "Four-Six Water Allocation" method. In the dry winter months, the natural river curve directs 60% of the water into the Inner River to ensure irrigation. Conversely, during the summer floods, the water level rises and flows straight, directing 60% of the torrent into the Outer River to prevent flooding, securing the safety of the plains.

2. Feishayan (The Flying Sand Weir)

Following the Inner River downstream, you will encounter the Feishayan. On the surface, it looks like a simple low gap in the dike, but it serves a critical function as a relief valve.

Its primary job is flood discharge and desilting. It operates on the principle of "River Bend Circulation." The waterway here curves, creating a centrifugal force. When the water flow is heavy, the surface water (which is cleaner) flows into the irrigation intake, while the heavy sediment and rocks on the river bottom are thrown outward by the centrifugal force. These rocks "fly" over the low weir and into the Outer River, preventing the irrigation channels from getting clogged. It ensures that only clean, safe amounts of water enter the fertile plains.

3. Baopingkou (The Bottle-Neck Channel)

The final and most crucial component is Baopingkou. This acts as the throat of the system. It is a narrow channel cut directly through the hard rock of Yulei Mountain.

Before the invention of explosives, Li Bing and his team used a primitive yet effective thermal expansion method: they heated the rocks with fire and then doused them with cold river water, causing the stone to crack and split. This channel controls the inflow of water into the Chengdu Plain. It works in tandem with Feishayan; if the water level gets too high, the narrow Bottle Neck restricts entry, forcing the excess water to back up and spill over the Flying Sand Weir. It remains the "check gate" that has protected Chengdu for two millennia.

Cultural Landmarks: Temples and Bridges

Beyond the hydraulic engineering, the scenic area is rich in cultural heritage that honors the creators of the system.

Erwang Temple (Two Kings Temple) Perched on the mountain overlooking the river, the Erwang Temple is dedicated to Li Bing and his legendary son, Erlang. The complex features traditional architecture with grand halls and intricate sculptures. It is not just a place of worship but a repository of history, where stone inscriptions record the ancient principles of river management, such as "Deepen the Shoal, Lower the Weir". Climbing the stairs here offers a splendid panoramic view of the entire irrigation system.

Fulong Temple (Dragon-Taming Temple) Located on Lidui (the rock pile separated from the mountain to create the Bottle Neck), Fulong Temple is steeped in mythology. Legend holds that Li Bing subdued an evil dragon here during the construction of the weir. The temple houses a stone statue of Li Bing dating back to the Eastern Han Dynasty, a precious artifact that connects visitors to the man behind the miracle.

Anlan Suspension Bridge Spanning the Minjiang River is the Anlan Suspension Bridge, one of the Five Ancient Bridges of China. Historically made of bamboo and wood, it is now reinforced with steel but retains its rustic appearance. Walking across it is a thrilling experience as the bridge sways above the rushing waters, offering a dynamic perspective of the Fish Mouth and the divided river.

The Wisdom of Maintenance

The longevity of Dujiangyan is not just due to its construction, but its maintenance. The ancients established a rigorous annual repair system known as "Sui Xiu" (Annual Repair). Every winter, when the water level was low, they would cut off the flow to dredge the riverbed and repair the dikes using bamboo cages filled with stones (Zhulong) and wooden tripods (Machas),.

This tradition follows the six-character secret: "Shen Tao Tan, Di Zuo Yan" (Deepen the Shoal, Lower the Weir). This means the riverbed opposite the Flying Sand Weir must be dug deep to ensure flow, while the weir itself must be kept low to allow floodwater and sand to discharge easily.

Conclusion

Dujiangyan is more than a scenic spot; it is a living textbook of Chinese wisdom. It showcases how ancient engineers conquered nature not by opposing it with massive concrete walls, but by understanding and guiding it. As you stand by the roaring waters of the Fish Mouth or gaze at the narrow passage of the Bottle Neck, you witness a project that has fed a civilization for over 2,200 years. It is a profound reminder that true engineering brilliance lies in sustainability and harmony.