Spring Water and Natural water are to some extent overlapping categories,
though the precise definition varies between countries.
In the United States, natural drinking waters are defined as water from a
natural aquifer that has not been altered with any additives and has not had
any substantive compound removed (gross sediment filtering is allowed.) Natural
waters include those extracted from the earth by any mechanical means including
pumps which may be thousands of feet deep.
Spring water, is a natural water that flows to the surface of it's own accord
and is hydrologically connected and chemically identical to a nearby
visible natural spring.
Artesian spring water is spring water which emerges from the ground under
hydraulic pressure. Artesian springs are usually the result of a body of
groundwater being trapped or contained beneath an impermeable layer of
sediment and then emerging from a crack or horizontal bore-hole.
To further complicate matters, all of the above categories may also be still waters, or carbonated. Worse yet, some natural waters have a light natural carbonation. Others, are artificially carbonated with naturally occurring CO2, and others yet, are artificially carbonated with artificial fizz.
Mineral waters are typically those with more than 500 parts per million (PPM) of dissolved salts. Some of the famous old mineral waters are very highly mineralized with several thousand PPM dissolved solids. If you let one of these waters warm up, and let the fizz go flat they are almost undrinkable. But hey, some people swear by them.
I think the perfect spring water should come from a natural artesian spring, with a low but balanced mineral content, say 100 PPM, and a hint of natural carbonization in the form of bicarbonate. This will give the water a sparkle rather than a fizz and it will taste fresh and clean even if it's not ice cold when you drink it.
Those are the basics, and in the world of bottled water, believe me, that's
as good a place to stop as any.
Salud, y pesetas, y tiempo para gustarlo!
This is a node rescue, done in a hurry. I'll probably expand it when I get a chance.