Dujiangyan Irrigation System

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Du Jiang Yan (Simplified Chinese: 都江堰; Traditional Chinese: 都江堰; pinyin: du jiang yàn) is an irrigation infastucture built in 256 BC during the Warring States Period of China by the Kingdom of Qin. It is even older than the Great Wall of China. It is located in the Min River (岷江, mǐn jiang) in Sichuan Province (四川省, sì chuan shěng) China near the capital Chengdu (成都, chéngdu). It is still in use today and still irrigates over 5,300 square kilometers of land in the region.

1 Before Construction
2 Plan for a Dam
3 Problems Encountered
4 Results of Construction
5 Du Jiang Yan Today
6 See Also
7 External Links

[edit] Before Construction

Devastating annual floods plagued the people living by the the Min River. Qin official Li Bing (李冰，lǐ bing), who was the sent to Chengdu as an official, decided to do something about it. He investigated the river with some locals. He familiarized himself with the land forms and water flows, and found the source of the water. The waters melted from Mount Min at the beginnings of every summer, went into the Min River and flooded the farms.

Du Jiang Yan

[edit] Plan for a Dam

Li Bing decided to divide the river into two streams, allowing one stream to continue on its normal course, while the other stream would flow into the farmer's fields. But there was one big problem. The Yulei Mountains blocked the way to the Chengdu Plain. He had to break a path through a mountain. The rock was too hard to break. So he had men throw wood and grass on the rocks and set it on fire, then poured cold water over it. This made the hard rock crack so the men could remove it. This labor took 7 years and they finally made an opening through the mountains to the plains that is 20 meters (65 feet) wide. The peasants called it 宝瓶口, bǎo píng kǒu (Bottleneck).

[edit] Problems Encountered

Li Bing split the river into two parts, but the part that was suppose to flow into the fields was higher than the other side, so very little water went there. He changed his plan a bit. He decided to build a man-made island levee to seperate to two parts to force more water to go into the Bottleneck. Using the some concepts of physics, he made the man-made island curved so the water would travel faster. Building a man-made island in the middle proved hard also. Li Bing tried to construct the base using pebbles and clay, but the water washed it away. He tried using huge boulders, but when the floods came, even the huge boulders were scattered. Li Bing was stuck with this problem. One day, as he was walking by a small stream, he saw women had put some bamboo cages with clothes in the steam, waiting to be washed. Even fast waters didn't move it. This gave him a brilliant idea. He had men construct huge bamboo cages, each several dozen meters long, and placed boulders inside them. He made hundreds of these, and dropped them in the middle of the river. In this way, nothing could move it. With a solid foundation, he constructed a large island and connected it waith a bridge from the Yulei Mountain.

Place where the two streams divide. Simplified Chinese:鱼嘴 (Fish Mouth).

[edit] Results of Construction

With the dam finished, no more floods ever came. The irrigation made Sichuan the most productive agricultural place in China. Li Bing was loved so much that he became a god to the people there. On the east side of Du Jiang Yan, people built a shrine in rememberance of Li Bing.

[edit] Du Jiang Yan Today

Today, Du Jiang Yan has become a major tourist attraction. It is also the admiration of scientists around the world, because it has one ingenious feature. Unlike contemporary dams where the water is blocked with a huge wall, Du Jiang Yan still lets water go thorugh naturally. Modern dams do not let fish go through very well, since it is a wall and and the water levels are different. In 2000, Du Jiang Yan became a UNESCO World Heritage Site.