Dujiangyan Irrigation System

Dujiangyan (Chinese: 都江堰; pinyin: Dūjiāngyàn) 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 (Chinese: 岷江; pinyin: Mínjiāng) in Sichuan province, China, near the capital Chengdu. It is still in use today to irrigate over 5,300 square kilometers of land in the region. The Dujiangyan along with the Zhengguo Canal in Shaanxi Province and the Lingqu Canal in Guangxi Province are known as “The three great hydraulic engineering projects of the Qin Dynasty”.

Planning

During the Warring States period (406–221 BC;), people who lived along the banks of the Min River were plagued by annual flooding. Qin governor Lǐ Bīng investigated the problem and discovered that the river was swelled by fast flowing spring melt-water from the local mountains that burst the banks when it reached the slow moving and heavily silted stretch below.

One solution would have been to build a dam but Li Bing had also been charged with keeping the waterway open for military vessels to supply troops on the frontier,[4] so instead he proposed to construct an artificial levee to redirect a portion of the river's flow and then to cut a channel through Mount Yulei to discharge the excess water upon the dry Chengdu Plain beyond.

Construction

Li Bing received 100,000 taels of silver for the project from King Zhao of Qin and set to work with a team said to number tens of thousands. The levee was constructed from long sausage-shaped baskets of woven bamboo filled with stones known as Zhulong held in place by wooden tripods known as Macha. The massive construction took four years to complete.

Cutting the channel proved to be a far greater problem as the tools available to Li Bing at the time, prior to the invention of gunpowder, were unable to penetrate the hard rock of the mountain so he used a combination of fire and water to heat and cool the rocks until they cracked and could be removed. After eight years of work a 20 metres (66 ft) wide channel had been gouged through the mountain.

Legacy

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 Dujiangyan, people built a shrine in remembrance of Li Bing.

Li Bing’s construction is also credited with giving the people of the region a laid-back attitude to life; by eliminating disaster and insuring a regular and bountiful harvest, it has left them with plenty of free time.

Today, Dujiangyan has become a major tourist attraction. It is also admired by scientists from around the world, because of one feature. Unlike contemporary dams where the water is blocked with a huge wall, Dujiangyan 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, Dujiangyan became a UNESCO World Heritage Site.

2008 Sichuan earthquake

On May 12, 2008 a massive earthquake centred on the Dujiangyan area struck. Initial reports indicate that the Yuzui Levee was cracked but not severely damaged.

Irrigation Head

Li Bing’s Irrigation System consists of three main constructions that work in harmony with one another to ensure against flooding and keep the fields well supplied with water:

The Yuzui or Fish Mouth Levee, named for its conical head that is said to resemble the mouth of a fish, is the key part of Li Bing’s construction. It is an artificial levee that divides the water into inner and outer streams. The inner stream carries approximately 40%, rising to 60% during flood, of the river’s flow into the irrigation system whilst that outer stream drains away the rest, flushing out much of the silt and sediment.

The Feishayan or Flying Sand Weir has a 200 m-wide opening that connects the inner and outer streams. This ensures against flooding by allowing the natural swirling flow of the water to drain out excess water from the inner to the outer stream. A modern reinforced concrete weir has replaced Li Bing’s original weighted bamboo baskets.

The Baopingkou or Bottle-Neck Channel, which Li Bing gouged through the mountain, is the final part of the system. The channel distributes the water to the farmlands to the west, whilst the narrow entrance, that gives it its name, works as a check gate, creating the whirlpool flow that carries away the excess water over Flying Sand Fence, to ensure against flooding.

Anlan Suspension Bridge

Anlan or Couple's Bridge spans the full width of the river connecting the artificial island to both banks and is known as one of the Five Ancient Bridges of China. Li Bing’s original Zhupu Bridge only spanned the inner stream connecting the levee to the foot of Mount Yulei. This was replaced in the Song Dynasty by Pingshi Bridge which burned down during the wars that marked the end of the Ming Dynasty.

In 1803 during the Qing Dynasty a local man named He Xiande and his wife proposed the construction of a replacement, made of wooden plates and bamboo handrails, to span both streams and this was nicknamed Couple’s Bridge in their honour. This was replaced in 1970 by a modern bridge of reinforced concrete and steel chains that is now opened to visitors.

Two Kings Temple

Erwang or Two Kings Temple is located on the bank of the river at the foot of Mount Yulei. The original Wangdi Temple built in memory of an ancient Shu king was relocated and so locals renamed the temple here in honour of Li Bing and his legendary son whom they had posthumously promoted to kings.

The 10,072 m2 Qing Dynasty wooden complex conforms to the traditional standard of temple design except that it does not follow a north-south axis. The main hall, which contains a modern statue of Li Bing, opens up onto a courtyard facing an opera stage. On Li Bing's traditional birthday, 24th day of the 7th month of the lunar calendar,local operas were performed for the public, and on Tomb Sweeping Day a Water Throwing Festival is held.

The rear hall contains a modern statue of the god Erlang Shen who was allegedly Li Bing’s son, but historic records fail to confirm this and it is possible that he was invented by locals to give their hero a descendent to maintain his family heritage. Guanlantin Pavilion stands above the complex and is inscribed with wise words from Li Bing such as, When the river flows in zigzags, cut a straight channel; when the riverbed is wide and shallow, dig it deeper.

Dragon-Taming Temple

Fulonguan or Dragon-Taming Temple in Liudi Park was founded in the third century in honour of Fan Changsheng, the Jin Dynasty founder of Tianshi Daoism. Following Li Bing’s death a hall was established here in his honour and the temple was renamed to commemorate the dragon fighting legends that surrounded him.

It is here that Erlang Shen, the legendary son of Li Bing, is said to have chained the dragon that he and his 7 friends had captured in an ambush at the River God Temple when it came to collect a human sacrifice. This action is said to have protected the region from floods ever since.

During the East Han Dynasty a statue of Li Bing was place in the river to monitor the water flow, with the level rising above his shoulders to indicate flood and falling beneath his calves to indicate drought. Recovered from the river in 1974 and placed on display in the main hall, this is the oldest known stone statue of a human in China.