我国南水北调的受水区是黄淮海平原和大西北两大区域和关中平原一小区域。向这三个区域调水的南水北调工程是一个统一的密不可分的系统工程。然而多年来我国研究南水北调时一直把东线、中线、西线看作是互相独立的３个调水系统 ,对这三个调水系统之间的互相依托和有条件替代的 The receiving water area of ​​the South-North Water Diversion Project in China is a small area of ​​Huang-Huai-Hai Plain and the two major northwest regions and the Guanzhong Plain. The South-to-North Water Diversion Project that transfers water to these three regions is a unified and inseparable systematic project. However, during the study of the South-to-North Water Diversion Project in our country, the East, the Middle and West lines have been regarded as three independent water diversion systems for many years. The three water diversion systems are mutually dependent and conditionally replaced