system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why don't we simply desalinate/clean ocean water for situations like droughts?
gpt
It's very expensive currently, and you have the problem of brine left over.  The process is not perfect so you don't end up with pure water on one side and salt on the other, you get about half salt-free water and the other half is doubly-salty water, or brine.  Disposing of brine is a problem.  It is usually put back into the ocean but it needs to be done slowly or it sinks to the bottom and raises the salinity at the ocean floor to dangerous levels for the creatures that live there.