PureInsight | November 5, 2001
The Dujiang Dam irrigation project is the oldest large-scale irrigation project in the history of the world. It has been supporting people in Sichuan Province, China, for more than 2,000 years. Why is the Dujiang Dam so durable?
People who have seen Dujiang Dam share the same impression: its general structure is very simple. The key part is the low bank in the middle of the Min River. It divides the river into the inner and outer rivers. Since the bank looks like a fish heading forward, people call the top part “fish mouth.” Water directed to the inner river reaches “treasure bottle mouth” about 1,000 meters downriver from “fish mouth.” This “treasure bottle mouth” is a twenty-meter wide artificial cut into Mount Yulei. It is called “treasure bottle mouth” because it looks like the mouth of a bottle. Water is directed east to irrigate the West Plain in Sichuan Province once it enters the mouth. Both sides of the watershed have protective banks made of scree. The inner side bank is called “inner Vajar bank.” The outer side is called “outer Vajar bank.” The banks are also called “golden banks.” At the end of the “fish mouth” watershed, there is a chamfer (sloping edge) to divert flood water and a “flying sand dam” to remove sand and control overflow.
The whole Dujiang Dam project was built on nature and completely dissolved in it. All things with a shape are living beings and have a life history. Their lives all have a process of formation, settlement and degeneration. When something can completely dissolve into nature, its life will certainly connect with nature. If nature does not degenerate, its life will not degenerate. These are all key factors in Dujiang Dam’s durability.
A more important factor, however, is human beings’ ability to live in harmony with nature. Once the Dujiang Dam was begun, people have protected the dam. It has also become a part of people’s lives.
The Dujiang Dam is mainly composed of “flowing cages.” These “flowing cages” are made of bamboo previously soaked in oil and lime. This pre-treatment enhances their fiber’s stretching force and resistance to rot. People make several one foot by more than three feet wide cages out of this pre-treated bamboo. Then they fill the cages with scree to build “flowing cages.” Every year people check them and replace the decaying cages with new ones.
Maintenance has been done on the dam annually since it was first built. When building Dujiang Dam, Li Bing, one of the dam’s founders, put a stone meter in the inner river to be used as the depth gage for removing sand during annual maintenance. The principle of this maintenance was to “dig sands deep and build dams low.” “Dig sands deep” just means to dig down to the level of the stone meter. Otherwise, the water volume in the inner river will not be enough for irrigation. “Build dams low” means that the dam can not be built too high. Otherwise it might cause problems diverting floods and overflow.
Maintenance begins every year during at the time of first frost. Water is stopped on the west side of “fish mouth” by putting “mazha” (name of the water-stopping mechanisms) in the outer river. All water is directed into the inner river. Then people dig out the sand that has settled on the irrigation chamfers of the outer river. In the spring, all the water is diverted into the outer river. Then people dredge the chamfers of the inner river and on the “flying sand dam.”
The annual maintenance is completed every year before the Qingming Festival in early spring. A big ceremony is held called “unleashing water.” At that time, the “mazha” are removed, and water again starts running through the channels and irrigating the plains. The ceremony is an exciting but solemn occasion with firecrackers and Chinese music. After unleashing the water by breaking the “mazha” there are many rituals. Workers tap the water with bamboo sticks, telling the water “not to destroy bridges and to follow the chamfers.” Young people knock at the “head of the water” with stones. People drive ducks into the water and young people all go into the water to catch the ducks. Old people fetch the “first flow of water” to pay respect to the Gods. This ceremony is not to celebrate victory over nature, but to express a sort of gratitude to the water and respect to the gods.
When human beings and nature care about each other, humans are then living in harmony with nature, in contrast to the ridiculous idea of “manpower overrides the heavens.” However, this principle seems to be easily abandoned in this era of modern science. The lesson seems so simple, but it’s very profound. During the civil war, many irrigation experts from Germany, England, France, America and other western countries came to visit Dujiang Dam. They thought replacing “flowing cages” was too troublesome. They proposed to build a concrete dam using principles of modern mechanics. But the concrete dam collapsed soon after it was built. Experts had to restore the original dam, using Li Bing and his son’s old way. It is fortunate that people didn’t succeed in changing the dam, so that this inter-living and inter-caring relationship between humans and nature could continue.
Dujiang Dam gives us meaningful inspiration. Ancient people believed that rivers have spirits and are alive. They never treated Dujiang Dam as a tool to control and change the river and override nature. Instead, they treated the dam as a part of nature – a life existence that was connected with people. The project was no more than one that diverted water using existing conditions. In fact, changing and controlling nature is an illusion rendered from not believing in gods. It is bound to fail. Actually, the so-called “nature” is not really natural. Everything is arranged by heaven and will not change according to man’s wishes. If people really alter nature willfully, the result will not be trouble-free. Natural disasters are caused by violating heavenly rules.