Older waterways and Sui expansion
Regional canals and navigation works existed before Sui. Following reunification, the dynasty dredged, linked and expanded them on a large scale, chiefly in the early seventh century. Waterways joined transport between river systems and more directly connected centers such as Luoyang with the Huai, Yangzi and southern regions. Separate local works entered a state transport system.
Connecting the canal routes
The Tongji Canal connected the Luoyang region with the Huai, renovated Hangou linked onward to the Yangzi, and southern waterways were expanded. In the north, the Yongji Canal supported the movement of supplies and forces. Routes followed rivers, terrain and political needs. Ships and transfers between reaches, supported by cities, storage and bankside facilities, sustained long-distance transport.
Grain transport and the labor of construction
Waterways connected grain-producing regions, urban populations and administrative centers, making state grain transport important for supply. The canals served courts, armies and building works while changing the movement of people and goods along their routes. Construction required large-scale labor, and operation required dredging, bank repair and water-level management. Building, transport and maintenance remained connected activities.
A network built over successive periods
Tang and later dynasties continued using, rebuilding and maintaining the canals. Routes changed with capitals, river courses and supply needs, and settlements and transport facilities developed through continued use. Sui expansion provided an important foundation for north–south movement. Later additions and management practices left the present Grand Canal with historical layers from different periods.