DU JIANG YAN IRRIGATION SYSTEM

'Du Jiang Yan' () is an irrigation infra-structure built in 256 BC during the Warring States Period of China by the Kingdom of Qin. It is located in the Min River (岷江, Mǐn jiāng) in Sichuan Province, 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.

Contents

Before Construction

Plan for a Dam

Problems Encountered

Results of Construction

Du Jiang Yan Today

See also

External links

Before Construction

Devastating annual floods plagued the people living by the Min River. Qin official Li Bing (李冰，lǐ bīng), who was 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.

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 'Mountain' (a rocky hill) blocked the way to the Chengdu Plain. He had to break a path through the hill. The rock was too hard to break. So he had men throw wood and grass on the rocks and set it on fire, and then pour 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 hill to the plains that is 20 meters (65 feet) wide. The peasants called it 宝瓶口, bǎo píng kǒu (Bottleneck).

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 separate to two parts to force more water to go into the Bottleneck. Using 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 of the river also proved difficult. Li Bing tried to construct the base using pebbles and clay, but the water washed them away. He tried using huge boulders, but when the floods came, even these were scattered. Li Bing was stuck with this problem. One day, as he was walking by a small stream, he saw women had put in the stream bamboo cages with clothes waiting to be washed. Even fast waters didn't move them. 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 by a bridge to the Yulei 'Mountain'-

Results of Construction

After the system was finished, no more floods occurred. 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 remembrance of Li Bing.

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 through naturally. Modern dams do not let fish go through very well, since each dam is a wall and the water levels are different. In 2000, Du Jiang Yan became a UNESCO World Heritage Site.

See also

★ Chengdu

★ Li Bing

★ Mekong

★ Warring States Period

★ Sichuan

★ State of Qin

★ UNESCO World Heritage Sites

External links

★ Du Jiang Yan and Chengdu in the LA Times

★ Photographs of Du Jiang Yan