Page "4th century BC" Paragraph 34

* Starting in the year 309 BC, the later Chinese historian Sima Qian ( 145 BC – 90 BC ) wrote that the Qin-employed engineer Bi Ling of the newly conquered State of Shu in Sichuan had the shoulder of a mountain cut through, making the ' Separated Hill ' that abated the Mo River, and excavated two canals in the plain of Chengdu.

The significance of this was phenomenal, as it allowed the new Guanxian irrigation system to populate an area of some 40 by 50 miles ( 60 × 80 km ) with over five million people, still in use today ( Needham, Science and Civilization in China, Volume 4, Part 3, 288 ).