Of the water present on the planet, 97% is salt water which is unusable for drinking or agriculture. Of the 3% freshwater, 68.7% is locked in glaciers. So, 1% of the water on the planet is liquid and most of that is underground. We don't really have a lot and things like fertilizers damage what we have.

It turns out that the amount of fresh water is relatively constant. If we want more in places that have less then we have to manufacture it from seawater, steal it from our neighbors by cloud-seeding, or rely on the weather cycle convert seawater into fresh water and then distribute it.

If you live in Dubai, you aren't waiting for it to rain. You're building desalination plants and processing seawater.