eli5: Why does there continue to be water in a river, even though it doesn’t rain all the time in the upper parts?

Question

eli5: Why does there continue to be water in a river, even though it doesn’t rain all the time in the upper parts?

In: 29

Answer 1

It’s called base flow.

Basically there’s a bunch of water underground. It seeps into the rivers. So, usually it’s a combination of the water cycle and base flow. But when the water cycle is interrupted (drought), the base flow is still running.

So you get lower water levels, but still running.