如果追溯到地质年代,整个淮北平原包括豫东、皖北、苏北都是黄河泥沙淤积而成(下游南岸受长江泥沙淤积)。淮河中下游与黄河下游同样在黄土冲积平原上形成,是黄土流失的产物,他们是孪生姐妹。黄土高原生成于第四纪,因此这两条河也都已有百万年的发育历史。苏北里下河是黄河与长江两个三角洲向海延伸扩大闭合而成的内陆碟形盆地,是泻湖的遗迹。有史以来,黄水虽曾多次南决入淮,其间也有夺泗、汴入淮的,但水路分歧,淮 If dating back to the geological era, the entire Huaibei Plain, including the eastern part of Henan, northern Anhui and northern Jiangsu, are all sediments from the Yellow River (the south bank of the Yangtze River is affected by the sedimentation of the Yangtze River). The middle and lower reaches of the Huaihe River and the lower reaches of the Yellow River are also formed on loess alluvial plain, which is the product of loess loss. They are twin sisters. The Loess Plateau was formed in the Quaternary, so these two rivers also have millions of years of development history. The Lixia River in the north of the basin is an inland basin formed by the extension and enlargement of the Yellow River and the Yangtze River to the sea, and is the remains of the lagoon. Historically, although the Yellow River has repeatedly decided to go south into Huai, during which time it also won the Sui and Huai into the Huai, but the waterway divergence, Huai