Dujiangyan: The 2,200-Year-Old Chinese Irrigation System That is Still Used Today!
The oldest irrigation system in the world is in China. Called Dujiangyan, it is also the only surviving monumental non-dam irrigation system from the ancient past. A marvel of Chinese science and engineering, Dujiangyan was built over 2,200 years ago. This system is still used to irrigate over 668,700 hectares of farmland, drain floodwater, and it provides water resources to more than 50 cities in the Sichuan province today.
The ‘Fish Mouth’ levee. Part of the Dujiangyan irrigation system. (CC0)
Dujiangyan is the brainchild of Li Bing, a local official of Sichuan Province over two millennia ago. It arose to confront the frequent flooding of the Minjiang River, a tributary of the Yangtze River. Li Bing and his son discovered the river was overflowing due to spring melt-water coming from the mountains which burst the banks of the slow-moving waters below. A dam was out of the question as Li Bing had been told to keep the waterway open for military vessels. Thus, Li Bing’s solution was to create an artificial levee which could move some of the water to another area and then make a channel in Mount Yulei to send the excess water to the dry Chengdu Plain.
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Ancient devotional statue of Li Bing on display at Dujiangyan, China. (CC BY SA 4.0)
King Zhao of Qin funded Li Bing’s project and tens of thousands of laborers were put to work. They built the levee by creating long sausage like baskets of bamboo filled with stones, known as Zhulong. These were held in place with wooden tripods called Macha. Natural topographic and hydrological features aid the system in irrigation, draining sediment, controlling flooding, and controlling water flow. No dams were required.
Traditional levee made of long sausage-shaped baskets of woven bamboo filled with stones known as Zhulong, held in place by wooden tripods known as Macha. (CC BY SA 4.0)
One of the most amazing features of the engineering project was the creation of a channel through Mount Yulei. It is worth noting that workers did this before gunpowder and explosives were invented. Li Bing’s solution to cut through the hard rock was to use a combination of fire and water to intermittently heat and cool the rocks until they cracked and could be more easily removed. It took eight years to create a 20 meter (65.62 ft.) wide channel through the mountain.
The completion of the system brought an end to flooding in the area and helped make Sichuan the most productive agricultural region in China. Li Bing’s ambitious project is now recognized as the 'Treasure of Sichuan.'
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Dujiangyan irrigation system tour map. (CC BY SA 4.0)
Scientists continue to admire Dujiangyan today for one particular feature – the harmonious way it manages water for humans yet enables ecosystems and fish populations to continue naturally. This stands apart from dams which block up and alter nature’s ways.
Dujiangyan is now a UNESCO World Heritage Site and it underwent a major renovation in 2013.
Dujiangyan helps humans control waterflow in a more natural way. (CC0)
Top Image: South Bridge, Dujiangyan, Sichuan, China. Source: CC BY SA 3.0