n 218 BC, half a million Qin soldiers were stranded in the far south of China, cut off from their food by the Nanling Mountains. The solution was a canal that carried boats across a continental divide — and parts of it still water the fields of Xing'an today.

This is the story of the Lingqu Canal: the Plowshare that splits a river, the Balance Weirs that tame its floods without a single gate, the winding South Canal, and the Doumen flash locks that came a thousand years later.

CHAPTERS
0:00 A canal that crossed a mountain
0:32 The War in the South
1:37 The Wall
2:19 Shi Lu
2:57 The Saddle
3:47 The Plowshare
4:38 The Balance Weirs
5:33 The South Canal
5:59 The Doumen
7:24 The Twist
8:02 Legacy

SOURCES
Huainanzi 淮南子, "Renjian xun" 人间训 (five armies, 500,000 men, Tu Sui, supply failure)
Sima Qian, Shiji 史记, "Pingjin hou Zhufu liezhuan" 平津侯主父列传 ("使监禄凿渠运粮")
Xin Tang Shu 新唐书, Treatise on Geography (Li Bo, 825; Yu Mengwei, 868)
Song Shi 宋史, biography of Qiao Weiyue 乔维岳 (pound lock, 984)
Joseph Needham, Science and Civilisation in China, Vol. 4 Part 3
Map data: Natural Earth (public domain)
Diagrams are schematic and not to scale. Figures such as the 70/30 split and the weir lengths are traditional or commonly cited approximations.


TAGS
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Lingqu Canal, 灵渠, ancient China, Qin Shi Huang, ancient engineering, canal locks, flash lock, pound lock, Chinese history, history documentary, hydraulic engineering, Guilin, Li River, Xing'an, Nanyue, Zhao Tuo, Joseph Needham