Here’s a couple of pictures of where an underground stream resurfaces.
The whole area of northern Arkansas and southern Missouri is lousy with limestone and caves. Sink holes are common, and occasionally one will open up and swallow a house.
Ground level is not sea level.
These things are underground, but above sealevel.
Oops.
Pressure is the key. The mass of water above sealevel puts enough pressure into the channel to be able to push water out below sealevel. The largest part of such a channel would be above sealevel, though underground.
I had a little training in caving, and one of my brother is a trained spelunker. And a cave isn’t just “a hole in the side of a mountain”.
In regions where caves are common (it depends on the local geology, as explained above), they have been holed up by subterranean rivers (not necessarily large rivers…a little stream can hole up a big and long cave over time by dissolving the limestone) . Some are “dead” (meaning that the water doesn’t flow anymore) some are active (there’s still water flowing…permanently or occasionnally during floods). Some are both (the water used to flow at a given place, but holed its way deeper or to other galleries, so you’ll find a “dead” cave network where the water used to flow, and an “live” one below it, or beside it)
They definitely aren’t mere “holes”. Though a lot of caves are very little (at least the part which can be explored), many are very large, with a complicated maze of galeries, sometimes several miles long, huge “rooms” (I mean that you could put a cathedral in some of them…but even if those are rare, a room which could contain an average house is very common), and can be hundred of feets deep. A lot of them aren’t fully explored (some are difficult to access to) and usually you just can’t explore them fully because the galleries are too narrow, or blocked (though you can blow up or enlarge these galleries, and it’s sometimes done in order to complete the exploration).
Seeing water flowing, or lakes, in these caves, is extremely common. Often just a very little stream of water, but sometimes a quite impressive river. Cave diving is sometimes needed (and quite dangerous) to explore a cave network when a gallery is below water level at all times. By the way, that’s why spelunkers usually check the weather forecast, since many caves can be flooded after a rainstorm. You don’t want to be crawling in a long and narrow gallery and suddendly notice that there’s more and more water flowing.
Quite often, when nobody knows where the flow of water is going, the method used is quite simply to drop colouring in the stream and then wait for coloured water to appear somewhere. Usually, it happens that the stream end up in some local spring. Sometimes, nobody knows. The stream probably ends in some subterranean reservoir.
And by the way, caves are rarely found “in the side of a mountain”. Most commonly, cave entrances are a hole or chasm (sometimes tiny and barely noticeable, sometimes gigantic, sometimes a dozen of feet deep, sometimes hundreds of feet deep) on a flat ground (usually caused by a collapsing of the cave ceiling), or situated on the side of a cliff.
Aquifers provide deep well irrigation water for the vast area of West Texas and East New Mexico. Irrigation wells have pulled water from these aquifers since the late 40’s. The output of these wells have dropped over the years but they still supply millions of gallons of water daily to this normally dry farm land.
No kidding. The discussion here is not about the existence of aquifers.
Once again, aquifers are NOT underground rivers!
As well as the underground rivers in limestone caves, particularly around Malham Tarn,
here in Yorkshire we have ‘dry valleys’, also in limestone country which have rivers beneath the soil at the bottom of the valley, except in times of flood, when the river is visible…
Waterdale is an example of such a phenomenon… but you can clearly see where the river should be.
Do dowsers limit themselves to limestone country, or do they imagine these things exist everywhere?
I’ve been caving in southern Ontario in a cave system that is pretty much dry in the late summer but runs as part of a river in the spring.
Now we hear from MR SMART… or he thinks he is.
You must think you own this forum. 
If you had paid attention to my post you would have noticed it was in answer to a post, posted by ** krisolov**.
**
FYI:
aq·ui·fer [ ákwifr ] (plural aq·ui·fers)
noun
water-bearing rock: a layer of permeable rock, sand, or gravel through which groundwater flows, containing enough water to supply wells and springs. **
robby,
This would be a better place without people like you. :rolleyes:
I would refer you to **Pantelle’**s excellent reply-
so it can be sometimes, but apparently rare outside limestone areas.
Pantellerite, sorry
it’s a long time since I studied any geology - didn’t recognise the reference
Tattle Creek.