If rivers flow from land and into the ocean, then where does that water come from?

Question

I’m essentially asking how a river “starts”, since I generally know that rivers mostly ends flowing into the ocean.

If you could, please use the Yangtze river as an example.

In: Physics

Answer 1

It’s all rain, or snow!

Rain falls across the land and flows down hill. It collects first into tiny rivulets, then into streams and creeks, and then into rivers which can merge with each other.

The same with snow, as it melts.

The region of land that collects all of the water into a particular river is refered to as that rivers “watershed”, because that land is shedding water into it.