Recently, the 2023 World Canal Congress seminar was held in Lingqu, Xing'an County, Guilin City, Guangxi Province. On the same day, the unveiling ceremony of the Lingqu World Cultural Heritage Archaeological Station was held in the Lingqu Museum of Xing'an County.
Founded in the Qin Dynasty, the Lingqu connecting the Yangtze River system and the Pearl River system is one of the oldest man-made canals in the world, with a history of more than 2,000 years, and still plays irrigation and flood control functions. In 2018, Lingqu was inscribed on the World Heritage List of Irrigation Engineering.
"In the canal projects throughout the ages, the Lingqu is impressive." According to Zhang Chuhan, academician of the Chinese Academy of Sciences and professor of Tsinghua University, as the "ancient pearl of water conservancy in the world", the spiritual canal has played an important role in unifying China and promoting Sino-foreign exchanges, laying an important foundation for the formation of the pluralistic and integrated pattern of the Chinese nation.
Text | Zhang Chuhan is an academician of the Chinese Academy of Sciences, an honorary director of the Chinese Hydraulic Engineering Society, and a standing director of the Chinese Dam Engineering Society
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A jewel of ancient hydraulic engineering
The territory of China at the end of the 3rd century BC was once divided.
Qin Shi Huang, who rose in the north, pacified the Six Kingdoms and included the Yellow River Basin and the Yangtze River Basin into the territory of the Qin Dynasty. In order to unify China, Qin Shi Huang sent troops to Lingnan, but he was confined to the high road of Lingnan Mountain, and the transportation of grain and grass was not smooth, and he could not attack it for a long time.
Lingqu, Xing'an County, Guangxi, June 30, 2019 (drone photo). Photo by Xinhua News Agency reporter Zhou Hua
In order to solve the supply problem, the Qin army investigated and found that there was a corridor between the mountains, where canals could be built. With the canal, it is possible to connect the Central Plains (Yellow River Basin, Yangtze River Basin) and Lingnan Region (Pearl River Basin) into a water transport network.
Qin Shi Huang decided to dig a canal between the mountains to connect the Xiang and Li rivers. In present-day Xing'an County, Guangxi, the Qin army dug the Lingqu, and the Yangtze River system and the Pearl River system were finally connected. Grain and grass were continuously transported from the Central Plains through the Lingqu to Lingnan, and Qin Shi Huang finally pacified Lingnan.
This is the origin of the spiritual channel.
The completion of the Lingqu changed the situation of insufficient supplies for the Qin army, and Qin Shi Huang took advantage of this to pacify Lingnan, establish Guilin, Nanhai, and Xiangxun, and unify China.
For more than 2,000 years, the Lingqu, which connected the Xiangjiang River in the Yangtze River system and the Li River in the Pearl River system, has always been the main communication route between Lingnan and the Central Plains, and is an important node of the ancient Silk Road.
As a treasure of ancient water conservancy projects in the mainland, Lingqu, together with Dujiangyan in Sichuan and Zhengguoqu in Shaanxi, is known as the "Three Water Conservancy Projects of the Qin Dynasty", which has enabled the civilization of the Central Plains to exchange and collide with civilizations in other regions, and has made important contributions to promoting the economic and cultural integration between different ethnic groups and forming a unified country.
After the opening of the Xiang-Gui Railway in 1940, the role of Lingqu in shipping was gradually replaced, but it still undertakes the task of irrigation.
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"Father of the World's Locks"
The planning and design concept of Lingqu has a high level of scientific and technological innovation, is a model of using the law of river water movement, conforming to nature and living in harmony with nature, and is a pioneer in responding to the time, suitable place, promoting people and people, and is also fully in line with the theoretical concepts of modern engineering hydraulics, channel hydraulics and hydraulic architecture, which is worthy of careful summary.
An irrigation weir dam built on the Lingqu waterway in Xing'an County, Guangxi Province, June 8, 2017. Photo by Xinhua News Agency reporter Lu Bogan
Scientific site selection: The Yangtze River system and the Pearl River system are blocked by the Nanling Mountain Range. The ancestors investigated and found that there were two rivers in Xing'an County, the Li River, a tributary of the Pearl River, in the west, which flowed into the Pearl River from north to south; To the east is the Xiangjiang River, a tributary of the Yangtze River, which flows from south to north and flows in parallel here.
If you build a canal in Xing'an and connect the two rivers, you can open up the Yangtze River and the Pearl River system.
The nearest Li and Xiang rivers are more than 20 kilometers away in a straight line, and it was difficult to dig a 20-kilometer canal in the mountains under the technical conditions of the time.
After in-depth investigation, the ancestors found that there is a tributary of the Li River, called Shi'an Water, which is only 1.6 kilometers away from the Xiang River. This means that only 1.6 kilometers of waterway need to be dug to divert water from the Xiangjiang River into Shi'an Water and then connect to the Li River.
However, the water level of Shi'an here is 4.3 meters higher than that of the Xiangjiang River, and the cost of raising the water level of the Xiangjiang River is too high. The water level is 1.5 meters higher than that of Shi'an Water by 2.4 kilometers along the Xiang River, where dams are built to raise the water level and canals are dug to connect the Xiang and Li rivers.
Precise diversion: The ancestors built a barrage on the Xiang River, called the Tianping Dam. A balance dam consists of a large balance and a small balance, which form an obtuse angle. At the same time, at the junction of the large and small balances, a diversion stone embankment extending towards the center of the river was designed to smoothly divide the north and south canals.
The Tianping Dam flows water from the Xiang River into the north and south canals, dividing the water 3:7. The 3-minute flow passes through the South Canal to the Li River, the 7-minute flow passes through the North Canal to the Xiangjiang River, and the excess flow in the flood season overflows through the Tianping Dam and re-enters the Xiangjiang River.
In the event of a flood, the incoming water can overflow the dam and flow into the Xiangjiang River. A total of five lateral overflow weirs are set up on the channel to drain the flood water in the channel, which is known locally as the "discharge balance".
The key to the precise diversion of the Lingqu lies in two aspects, one is that the height of the overflow weir determines the upstream water level, and the other is that the overflow capacity of the north and south channels determines the 3:7 water dividing ratio. According to the 3:7 water division, the water depth of the north and south channels is basically maintained at 1.5 meters to adapt to ship transportation.
Downhill deceleration is conducive to navigation: under the overall layout of the canal head hub divided into north and south channels, the north channel turned two "S" shaped turns on the platform on the right bank of the Xiangjiang Old Road, and then flowed into the Xiangjiang River. The straight-line distance of the north canal from the inlet to the outlet is only 1.8 kilometers, but through the design of two "S" shaped large turns, the channel is extended to 3.25 kilometers, which can effectively reduce the specific drop and flow rate of the water, and can make the ship sail safely and smoothly without setting up a lock.
To sum up: artificial bending, extending the channel, reducing the flow speed, easy to navigate, water conservancy engineering called this scheme "curved generation lock", which is an innovation of ancient water conservancy technology, Lingqu is the earliest ancient canal using this technology.
A water conservancy facility was built to ensure safe navigation: in the Lingnan area, where the Lingqu is located, there is an 8-month flood period and a 4-month dry period a year. How to keep the spiritual canal open?
Ancient ancestors creatively built steep gates.
The steep gate of Lingqu is known as "the steepest in the world", and the steep gate technology was later applied to the Grand Canal and played an important role. In the 80s of the 20th century, experts from the International Commission on Dams came to Lingqu to investigate, and the experts of the committee gave a comment: "the father of the world's locks".
The canal is 37 kilometers long, and in the 11th century, there were up to 36 steep gates on the channel. The design of the steep gate fully considers the topography, water level and flow of the river, and the closest distance between the two steep gates is only 150~200 meters, and the longest distance is more than 2 kilometers.
When the boat going against the current enters a steep gate, close the steep door behind it to block the water, open the steep door in the forward direction, and sail forward after the water level is level, forming a prototype similar to a multi-stage lock. The steep gate of the Lingqu ensures the safe navigation of the channel for many years, and the steep gate engineering technology ensures the comprehensive goal of building gates in ancient rivers on the mainland to facilitate navigation, irrigation and water supply.
The results of the exploration of the Lingqu have influenced the Grand Canal, which in turn has influenced the mainland's successive water conservancy projects, such as the South-to-North Water Diversion Project, and its eastern route project is to use the expansion and extension of the Grand Canal route.
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New age values
In the 21st century, Lingqu has fulfilled its mission, but at the same time it has added strong new value over the years.
Tourists visit Lingqu, Xing'an County, Guangxi Province (pictured on June 7, 2017). Photo by Xinhua News Agency reporter Lu Bogan
Based on Lingqu, the literati Moke flourished in poetry, borrowed lyricism, and wrote many excellent literary and artistic works, taking only two books as examples.
Guilin-born writer Huang Jishu wrote the historical novel "Lingqu". Based on the historical figure Shi Lu, the novel tells the legendary story of his hardships and outstanding encirclement, opening up the Central Plains and Lingnan, connecting the Xiangjiang and Li rivers, and finally laying a solid foundation for the unification of the whole China by the Qin state. The novel is imaginative and has a broad vision.
Writer Gao Honglei's "History of the Other Half of China" is themed "tracing the ins and outs of China's 55 ethnic minorities and composing a magnificent epic of multi-ethnic joint opening up of the motherland", and a chapter on the spiritual canal: miracles often happen in times of helplessness, and potential is stimulated in moments of desperation. When Qin Shi Huang was anxious, a man named Shi Lu made a bold proposal: dig a canal between the Xiang and Li rivers to open up the two major water systems in the north and south.
Lingqu has promoted the exchange and integration of Lingnan culture and Central Plains culture, and has played an important role in the historical process of China's reunification.
As a landmark project to accelerate the construction of a powerful transportation country and a backbone project of a new land-sea channel in the west, the construction of the Pinglu Canal began on May 23. The Pinglu Canal connects the Xijiang Shipping Trunk Line with the Beibu Gulf Sea, and after completion, it will open a large river-sea combined transport channel from the main stream of the Xijiang River to the south into the sea in the southwest region of the mainland.
The Pinglu Canal starts from the mouth of the Pingtang River in Xijinku District, Hengzhou City, Nanning, Guangxi, and enters Beibu Bay along the Qinjiang River through Luwu Town, Lingshan County, Qinzhou, with a total length of 134.2 kilometers and a design annual one-way passage capacity of 89 million tons.
The project mainly includes the renovation of waterways, shipping hubs, water conservancy facilities and cross-river supporting projects along the route, with a total estimated project budget of about 72.7 billion yuan.
After the completion of the Pinglu Canal, the cargo from the southwest region will go to sea through the Pinglu Canal, shortening the voyage into the sea by more than 560 kilometers compared with the sea through Guangzhou, which is of strategic significance for promoting the development of Guangxi and the southwest region, and promoting the optimization and adjustment of the industrial layout along the route and the formation of the canal economic belt, helping to promote the large-scale development of the western region in the new era, forming a new pattern, and becoming a new coordinate for the new era.
The river rushes, day and night. The two major projects echo each other and are destined to write a strong mark in the history of China's water conservancy and Chinese civilization.
Editor's note: Regarding the Pinglu Canal, Uncle Ku has explained in detail, and interested friends can open "Guangxi Navigation into the Sea? A long-cherished wish for a century is finally coming true! " article in depth.
Source: Outlook Think Tank, Xinhua News Agency