As far as I know, many D&D spells were inspired by popular fantasy tropes, like priests' blessings and healing hands or wizards' fireballs and lightnings. However, the Create Water spell seems to stand out, in that it seems less archetypally associated with its class (clerics/priests) than the others.
It is neither a rainmaking ritual, nor a divination ability that helps to find water. It is an ability to make water appear out of nothing, and it's clerical for some reason. I can't remember any fantasy book or movie where clerics actually do that (aside from the ones being inspired by D&D).
Did the idea of priests/clerics having a water-creation ability come from an earlier source, or is it an original D&D invention, like the Cleric class itself?