How are waterfalls supplied with continuing water?

This post was in response to How Are Waterfalls Formed?

I understand your explanation and diagrams.

And understand how waterfalls are formed.

But my question is why does waterfalls continue running.

Pick at waterfall. I understand rain and snow makes water. But that couldn’t supply these waterfalls with continuing water.

Does the rain and snow keep adding to the basin supply of water already there.

And does the water level drop. If it doent rain or snow. Pick a waterfall.

Have anyone track, or trace and waterfall to see if it’s sharing water to other falls. And is the ocean’s water being filter to supply fresh water to the springs and lakes.

I’m not a student,I’m just curious.