I personally use RO water & salts to build my water. But if you're looking for mountain spring or the like to use as-is, then look around on the various company websites (or ask) for their water analysis information. I know arrowhead, for one, publishes theirs on their website. I'm sure other spring water companies likely follow suit.
I know that doesn't directly answer your question - but I don't have a direct answer. Still... knowing the exact water profile may be more useful in the end, and if it's not exactly what you want, you have a baseline upon which to judge which, if any, salt additions you might add.