Just so we're clear: fresh water is shifting location ... when it comes to the total available, it's increasing. There are many more locations were humans can now live where they couldn't a century ago, not less.
The issue is not that we can't live anywhere. The earth is greener than before. The issue is that there are a small number of locations where humans can't live anymore, especially not without good water management. Obviously, people don't want to or can't leave, and some of the locations that didn't use to, but now really do require proper management have a LOT of people.
Teheran has more water than a century ago. But more does not mean infinite.
The entire working mechanism of climate change is increased water in the atmosphere. That's why it's getting warmer. CO2 and other gases only accelerate that process a little bit (but as we're at the end of the warming cycle, "a little bit" should be interpreted as accelerating warming by a little bit, if you count the number of years it brings warming forward, that's a lot. Probably a millennium, maybe more). Obviously it also makes things warmer and generally wetter, thereby making very large areas livable that weren't livable before.
The entire inside of India used to be desert. That desert did not just reduce in size, it split in three pieces and two of them shrunk to zero, and even the third is turning green. The Sahara too is less than half the size it used to be.
On YouTube or Netflix, look up the Fresh Water episode of the Our Planet documentary series by David Attenborough, fresh water is disappearing all over the place due to our actions.
