"Water has size and distance. Water comes from the mountains and enters the sea, and its destiny is: to pass through the water. Water leads to other waters, and those who enter the flood and the sea are called branches of water. In the ditch of the mountain, where there is water, there is mother water, and life is called valley water. Water comes from underground and flows in floods and the sea, so it is called "Chuanshui". Those that come out of the ground and don't flow are called deep water. These five waters can go because of their benefits, so they can choke; There will be danger soon. "
Here, the rivers in the world are divided into five types according to their different sources and their different flows into the sea, rivers and rivers: refined, straight, ancient, Sichuan and Yuan. This paper puts forward the governance principle of water "benefiting its potential" and the viewpoint that choking for a long time is dangerous. These are all scientific and reflect the knowledge level of river geography at that time.