Later on, probably around 250 BC, the king of the state of Hann felt menaced by the expansion of the Qin. He sought to deflect the warlike ideas of the Qin by turning his dangerous neighbor’s energy toward peaceful projects:
“The state of Hann, learning that the state of Qin was fond of undertaking large projects, dispatched a water engineer named Zheng Guo to go to Qin and persuade the ruler to construct a canal from a point of the Jing river west of Mt Zhong to the pass at Hukou, and from there along the Northern Mountains east into the Luo River, a distance of over 300 li. Ostensibly the purpose of the project was to provide irrigation for the fields, though in fact Zheng Guo and the rulers of Hann hoped thereby to wear out the energies of the state of Qin so that it would not march east to attack Hann. Zheng Guo succeeded in getting the project started, but halfway through the real nature of the mission came to light. (…)
“The Qin ruler, deciding that this (the argumentation of Zheng Guo that the canal would benefit to the Qin) was sensible, in the end allowed him to go ahead with the canal. When it was finished, it was used to spread muddy, silt-laden water over more than 40,000 qing of land which up until this time had been very brackish, bringing the yield of the land up to one zhong
per acre (mu). As a result the area within the pass was converted into fertile land and no
longer suffered from lean years; Qin became rich and powerful and eventually was able to
3 5
conquer all the other feudal lords and unite the empire.”33
This canal, put into service in 246 BC, is more than 150 km long, and links the Jing to the Luo in Shaanxi (Figure 8.8). It is called the Zhengguo canal in honor of its builder, and supplies numerous secondary canals that provide gravity irrigation for the entire lower region. The canal has been rebuilt several times, even recently, with new intakes further up the course of the Jing to account for the progressive degradation of the river bed and the sediment deposits in the canal itself.
