An ancient engineering marvel

Imaginechina

Take a boat, and you can travel 2,000 kilometers from Beijing to Hong Kong, thanks to an ancient canal in the Guangxi Zhuang Autonomous Region — the Lingqu Canal. 

The Lingqu Canal completed more than 2,000 years ago is one of the oldest canals in the world.

Apart from serving as a water transportation route, it has also worked as an irrigation system and was included on the International Commission on Irrigation and Drainage’s Heritage Irrigation Structures list this year.

Sitting in Xing’an County in the Guangxi Zhuang Autonomous Region, the canal connects the Xiangjiang and Lijiang rivers, and consequently links the Yangtze River and Pearl River systems, creating a major transport waterway.

It was the first canal in the world to connect two river valleys and enabled boats to travel across China from north to south. 

The Lingqu Canal, one of the “three great hydraulic engineering projects of the Qin Kingdom” together with the Zhengguo Canal in Shaanxi Province and the Dujiangyan Weir in Sichuan Province, was a major factor in the Qin unifying China and building the Qin Dynasty (221-206 BC).

It was originally built at a supply route for the Qin army to conquer southern tribes. In 221 BC, the Qin Kingdom unified the six kingdoms of the Warring States Period (476-221 BC) to create the first dynasty of imperial China.

As a follow-up plan to unify China further, Qin Shi Huang — the first emperor of the Qin Dynasty — dispatched 500,000 troops southwards to crack down on the Baiyue tribes in south China. He ordered the construction of the Lingqu Canal, and Shi Lu was put in charge of the project as chief designer. With 100,000 soldiers led by Shi, the Lingqu Canal with an overall length of 36.4 kilometers was completed in 214 BC. Shortly afterward, Baiyue was conquered, thereby completing the unification of the Qin. 

The canal was the major water transport route between Lingnan (the lands in the south of the Nanling Mountains) and Central China until the completion of the Yuehan Railway and the Xianggui Railway.

It is still used for flood control and to irrigate about 65,000 mu (43 square kilometers) of farmland.

The Lingqu Canal actually comprises two canals — the North Canal connecting the Xiangjiang River and the South Canal running into the Lijiang River, as well as a series of hydraulic facilities

The North Canal, also known as the new path of Xiangjiang River, is about 3.25 kilometers long, while the South Canal runs 33.15 kilometers into the Lijiang River. 

‘Huazui’ – water dividing weir

The main design concept of the Lingqu Canal was to raise water from the Xiangjiang River by using weirs.

“Huazui,” a plowshare-shaped weir, is a major part of the system, sitting on the Haiyang River — a tributary of the Xiangjiang River— which divides the water flow. It diverts one stream through the South Canal into the upper branch of the Lijiang river and directs the other through the North Canal winding into the Xiangjiang River.

The original “huazui” was buried by accumulated silt, and moved to its current location about 100 meters downstream in the late 19th century. 

Big Balance and Small Balance

At the lower reach of the “huazui” lie the 124-meter “Xiao Tianping” (Small Balance) and 380-meter “Da Tianping” (Big Balance), as segments of the embankment at the South Canal and North Canal.

The two “Balances” form a V-shaped diversion dam and ease the impact of the water flow. They were named “Balances” for their capability of two-way control of the water flow.

When the water level falls, they can feed water into the canal to ensure the smooth progress of vessels. When the water level rises, they can divert water into the Xiangjiang River, and thus protect villages and crops from floods. 

‘Doumen’ — the earliest lock

The “doumen” on Lingqu Canal is probably the world’s earliest lock. After the canal was completed, it was still difficult to navigate in dry seasons with limited water. Thus, the first locks were built to raise and lower water levels to facilitate navigation.

It is not sure how many “doumen” were set in the Qin Dynasty, as there have always been new locks built and others abandoned. But the Northern Song Dynasty (960-1127) saw the most with 36.

The “doumen” — with a stone base and bamboo gate — were placed almost every kilometer. Troops, called “Dou Jun” (Dou Army) were stationed every day and night at each lock.

It is said that the first “Dou Army” was led by an officer surnamed Ji on Qin Shi Huang’s orders.

Together with his team and family, they settled at the first “doumen” and served for generations.

Some of their descendants took Doumen as their surname, which was later shortened to Dou. Although first built for military transportation, the Lingqu Canal also turned Xing’an County into a rich farming area through the large-scale irrigation.

The canal was repaired many times through centuries. It was again renovated and well preserved as an ancient project after 1949.

Although less important to navigation and irrigation today, it is still regarded as a national treasure for its innovative ancient design across mountains, its curved routes, locks and its comprehensive water control through its hydraulic features.