[ianai]

Except the earth includes minerals we probably don’t want to drink like asbestos, arsenic, radioactive isotopes, etc. The concentrations are going to vary wildly. Basically I’m sure deep well water and water from the surface will be exposed to vastly different things. I know, as a lifelong desert dweller who's almost exclusively lived off well water, that well water quality needs to be monitored and treated. My alma mater’s town had to stop using one well when arsenic tolerances were decreased, for instance.