But we must know that the research scope of water was limited at that time.

In other words, the water in the poem refers to liquid water.

"Don't you see how the water of the Yellow River flows down from the sky?" means rain.

"Entering the ocean and never coming back" also means that liquid water will not "return" directly in the form of liquid.

In fact, water will be transferred back as gas and stored as solid ice. The transmission of gas and water is easily overlooked by the ancients, so there is no need to worry at all. Our fresh water will be exhausted in vain.

Although poetry describes facts, it is not the whole truth.

In fact, the ancients knew that there was such a thing as water vapor, but the water list here in the poem refers to liquid water, without taking water vapor into account, which is intended to express an artistic conception, so it cannot be said that this poem is wrong. )