Mineral water contains ... wait for it .... minerals (!) (and I assume well water does too to some extent, though I know very little of that) so it should be fairly good to drink, assuming there is no pollution.
If you are drinking from a stream, a typical advice is to make sure there isn't a farm upstream, as there might be bad stuff in the water washing down from the fields (whether they use natural or chemical stuff on their fields)
Melted snow would also depend on the amount of pollition
and ps, since you asked what is "cleaner", Reg is correct, urine is clean, that it, it does not contain germs.
Nothing nasty about it, just a scientific fact (half my family are nurses, so I know weird stuff)