How do springs originate at the top of the hills and how do they acquire such volume of water?

Question

One explanation that I found was rainfall but it is not apparent that rainfall could contribute to such volume of water.

In: Geology

Answer 1

So, water above ground tends to pool into ponds and lakes that are basically flat on the top. But water below ground (called an aquifer) is not like a lake. It’s usually moving according to specific patterns.

One of those patterns is that the water on a hill tends to follow the shape of the surface. Kind of [like this](https://images.app.goo.gl/TA4qHBC8iBXjbHWo8) (disregarding the interpolation lines). Sometimes a large rainfall can cause the aquifer to fill up and the top of the aquifer (the water table) will meet the surface of the hill and you get a spring!

However, most hills aren’t just lumps of one material. So you can get interesting things like [a perched water table ](https://images.app.goo.gl/LhX78Xxh2Z4D63PN7). Which can lead to a spring.

One rule that water always follows, it that it prefers the path of least resistance. So if there is a channel that’s easier to follow, it might even flow uphill! Like [in this image](https://images.app.goo.gl/8tEu698FoucUGXi37), the water is filtering down into the rock (in this case granite) but suddenly there is a fault which causes there to be something like a pipe. All the pressure from the water being under the rock causes it to go spurting up through the crack. In the example image, the water went so deep and came up so fast it’s a hotspring! (But not a geyser, you need different conditions for geysers). If it came up more slowly, the heat would be lost and it would be a regular spring.

I apologize if this is closer to ELI15. But it’s a very complex subject. I suppose the ELI5 would be “when it rains, there’s lots of water and it comes out at the surface”.

If you like this stuff, check out hydrogeology.