 The less well known ancient Lingqu Canal, connecting the upper Xiang River with the headwaters of the Guijiang, allowed a direct water connection from the Yangtze Basin to the Pearl River Delta.Historically, the Yangtze became the political boundary between north China and south China several times (see History of China) because of the difficulty of crossing the river.This occurred notably during the Southern and Northern Dynasties, and the Southern Song.