The ancients called the Yangtze River a river and the Yellow River a river.

The water in the Yangtze River is clear, and the water in the Yellow River is turbid. The Yangtze River is flowing, and the Yellow River is also flowing.

An old proverb goes: When a saint comes out, the Yellow River becomes clear. But when will the Yellow River be cleared? The water of the Yangtze River irrigates the fields in several provinces on both sides of the river, and the water of the Yellow River also irrigates the fields on both sides of the provinces. It can only be used because the water is clear, and it can only be used not because the water is turbid. This has been true since ancient times.