In ancient Chinese water conservancy projects, in addition to Dujiangyan built by Li Bing and his sons in the Qin Dynasty, there are five other ancient weirs that have become World Heritage Sites, namely Tongji Weir in Lishui, Zhejiang, Tashan Weir in Ningbo, Zhejiang, Jiangxi Weir in Longyou, Zhejiang, and Hanzhong San in Shaanxi. Weir, Sichuan Leshan East Wind Weir.

Among them, Tongji Weir has set two world records: the world's earliest arch dam and the world's earliest overpass over water.

Tongji Weir

Tongji Weir is located at the edge of Yantou Village, Bihu Town, Liandu District, Lishui City, Zhejiang Province. It was built in 505 AD and has a history of more than 1,500 years. It is the oldest large-scale water conservancy project in Zhejiang Province.

In 2014, Tongji Weir was successfully selected as the World Irrigation Project Heritage. The World Irrigation Engineering Heritage is also a World Heritage category. Its selection criteria are extremely strict. It must meet the requirements of irrigation and drainage projects with a construction history of more than 100 years, and at the same time be ahead of the same era in terms of engineering design and construction technology. Currently, China has 13 world irrigation engineering heritage sites.

The water canals of Tongji Weir are distributed in the shape of bamboo branches. They are composed of three parts: main canal, branch canal and Mao canal. It passes through the entire Bihu Plain. After 1500 years, it still protects more than 30,000 mu of farmland in the largest granary "Bihu Basin" in southwestern Zhejiang. It is really a great water conservancy project to ensure the harvest from droughts and floods.

The world's earliest arch dam

Arch is a dam construction form widely used in water conservancy projects today. The earliest arch dams abroad are the Elqi Arch Dam built by the Spanish in the 16th century and the Bandardo Arch Dam built by the Italians in 1612. The Tongji Weir is more than 1,000 years earlier than their history.

Because the arched dam can transfer the load from the center of the dam to the two ends of the dam, thereby reducing the pressure on the center of the dam, when the flood surges, it happens to be affected by the natural gyration of the backflow of the Ou River, which weakens the flood’s impact on the dam. The impact force of the dam enhances the strength of the dam and makes the dam body as firm as a rock.

The world's first overpass over water

Tongjiyan Shihan is also called "overpass over water" by later generations. It was built in 1111 AD. This three-dimensional crossing diversion bridge built on Tongjiyan canal is commonly known as "three-hole bridge".

The stone bridge is divided into three levels, the upper, the middle and the lower. The middle layer is where muddy stream water flows directly into the Ou River from the bridge deck. The bottom layer is the clearer weir and canal water, which flows all the way to Tongji Weir.

Before the completion of the stone bridge, whenever a flash flood broke out, the gravel and pebbles carried by the flood would block the channel and block the weir water. In the Northern Song Dynasty, when science and technology were not yet developed, the ancients had such wisdom and construction technology, which really made the world. Admiringly.

The Tongji Weir "overpass over water" is nearly 900 years earlier than the Magdeburg Water Bridge built in October 2003 by the Germans for more than a century.

Many overseas architecture and water conservancy experts commented that: "When there was no overpass in the world, the Chinese people had built a water overpass in this mountainous township."

The southwest of Zhejiang Province, China is a hilly mountainous area with "Nine Mountains, Half Water and Half Field", inlaid with the Bihu Plain covering an area of about 60 square kilometers. It is precisely because of the existence of Tongji Weir since ancient times that Bihu Plain has been called the land of fish and rice. If you have the opportunity, you may wish to take a look at this ancient weir. Editor/He Yuting