system
Given the following post, respond as if you're commenting on Reddit:
human
Why does an oasis in a desert not just evaporate?

I don’t see how it can flourish so damn well.
gpt
It does evaporate. It’s just that more ground water keeps flowing in to replace it. Bodies of water at the Earths surface can get water from the mantle (via volcanic venting), from rain, from rivers (really mostly rain), and from groundwater. In the desert, water from rain and rivers is minimal. If there’s no volcanic vent, then the water for the oasis must be coming from groundwater flow.