An Engineer from Han and a Project for Qin
The “Chronological Table of the Six States” in the Shiji records the start of work on the Zhengguo Canal in the first year of King Zheng of Qin, 246 BCE. This year is an appropriate marker for the beginning of the project; the record does not supply an exact completion date for the entire canal. Its director, Zheng Guo, was a hydraulic engineer from the state of Han. Amid competition in the late Warring States period, his water-diversion expertise became entangled in interstate political schemes.
The Shiji’s “Treatise on Rivers and Canals” states that Han sought to consume Qin’s manpower and wealth in a major project, delaying military campaigns eastward, and therefore sent Zheng Guo to persuade Qin to build the canal. The plan was exposed partway through construction, and Qin intended to execute him. He argued that the completed canal would also benefit Qin, and the work ultimately continued. The account distinguishes original intent from actual outcome: a scheme to delay war became an investment in Qin’s own agricultural heartland.
Diverting the Jing toward the Luo along the Northern Mountains
The canal took water near Hukou, where the Jing emerged from the mountains, and ran east along the southern foothills of Guanzhong’s northern ranges, eventually reaching the Luo River. The histories give its length as more than three hundred li. This is an ancient route measurement, not a modern distance in kilometers that can be obtained without considering the historical unit, changes in alignment, and the scope of investigation. Following higher ground along the foothills was crucial: maintaining elevation allowed the water to flow toward lower land to the south. The relative heights of the intake, main canal, and fields had to work together, progressively using the head available at the inlet along the route. The alignment therefore determined which fields could receive water and which plots required other arrangements.
Combining texts and topography, Li Lingfu notes that the Zhengguo Canal also crossed south-flowing rivers including the Ye, Qing, and Zhuo. Maintaining a long east–west canal required managing those intersections and drawing on water encountered along the route. Diversion weirs and linked canal reaches are explanations researchers propose from historical river conditions; specific installations still need to be matched with physical remains. The long canal’s value lay in connecting dispersed water sources with land that could be developed.
How Sediment Became a Resource
The Jing carries large quantities of sediment. The canal introduced its turbid water into low-lying saline-alkaline land, depositing fine soil and improving conditions through water supply and drainage. This silt irrigation combined land creation, soil improvement, and watering, differing from supplementary irrigation tailored to crops on established farmland. Sediment could be a resource but could also choke the canal. Benefits depended on where water entered, how long it remained, and whether canals and fields could continue to drain. Farmers benefited both through the current crop and through gradual improvement of field surfaces and cultivated soil. Once flow escaped control, the same sediment could accumulate in the canal and prevent water from reaching downstream land.
The Shiji states that the completed canal irrigated more than forty thousand qing, producing one zhong of grain per mu, and describes Guanzhong as fertile land. These figures and assessments express an ancient author’s understanding of the project’s achievements; they are not modern statistics compiled field by field. The claim of “no bad harvest years” should likewise be understood as a broad characterization of abundance, not proof that drought never returned.
Land Development and State Mobilization
Excavating the main canal was only one part of the undertaking. Water reaching the fields still required branch channels, distribution within fields, and continuing dredging and maintenance. Earthmoving, transport of materials, and labor allocation had to be coordinated with cultivation and other service obligations. The histories do not preserve enough evidence to reconstruct daily construction organization, but a canal of this length demonstrates that engineering expertise needed support from labor and supplies on a large scale. Management after construction also concerned the distribution of burdens: upstream water use affected downstream users, and the timing of repairs affected household farming. Continuing benefits required an order governing these relationships.
The Hanshu records Emperor Wu, when discussing water management, calling for encouragement of agriculture, full use of the land, and equitable arrangements for labor service and water distribution without disrupting the farming calendar. Although a Han directive, it concretely illustrates the affairs involved in operating a large irrigation district over time. More cultivable land and steadier grain supplies could strengthen Guanzhong’s economic base. Qin’s conquest of the six states also involved military affairs, institutions, and interstate relations; the Zhengguo Canal was one of its material conditions.
The Six Auxiliary Canals, the Bai Canal, and Later Changes
In the sixth year of Emperor Wu’s Yuanding era, 111 BCE, Ni Kuan (兒宽) proposed constructing the Six Auxiliary Canals to extend irrigation to higher ground beside the Zhengguo Canal. In the second year of Taishi, 95 BCE, Bai Gong proposed the Bai Canal, diverting the Jing toward Yueyang and ultimately into the Wei. The Hanshu gives the latter a length of two hundred li and an irrigated area of more than 4,500 qing. These additions show Han water management continuing to adjust the areas benefiting from earlier development.
Later projects drawing on the Jing inherited this experience but repeatedly altered intakes and canal networks. Riverbed incision could leave older intakes unable to draw water, sediment accumulation demanded repeated dredging, and floods could damage crossing structures. The relationship among the Zhengguo and Bai canals and the much later Jinghui Canal therefore lies in continuity of water use, irrigation-district management, and canal-maintenance experience. Distinguishing the projects makes it possible to see how each period addressed the relationship between water and land anew.