I live in NYC and was recently surprised to learn that despite the population, we don't rely at all on desalination. Pure water catchment. Good YT doc on this: https://www.youtube.com/watch?v=IDLkOWW0_xg
https://www.nyc.gov/html/nycwater/html/drinking/reservoir.sh...
Problem is that people don't want to live in places that have winter, so they dogpile in California, Arizona, etc.