A saucer in the floodplain
The Lixia River (Lixiahe) region of Jiangsu province is is not a river; it is a vast, low-lying alluvial plain. Geographically, it forms a saucer-shaped depression, with the center of the plain sitting at an elevation of only about 1 meter, while the land surrounding it is higher, at around 4.5 meters. This unique "pot bottom" topography makes the area naturally susceptible to severe flooding. Historically, it was a catchment for waters from the Huai River and the Yangtze River, as well as local rainfall, leading to a reputation for having floods in nine years out of every ten.
To manage this constant water threat across 50,000 square kilometers, engineers constructed a complex water conservancy system. The network includes more than 2,000 flood control gates, thousands of kilometers of levees, and numerous pumping stations. This infrastructure manages floodwater and actively manages and redistributes it. During periods of heavy rainfall or high river levels, the system can divert water from threatened areas to other parts of the network with more capacity, or discharge it into the Yangtze River or the Yellow Sea. The entire system of canals and rivers in the region stretches over 12,000 kilometers.