I can't answer that, but for a long time, there have been predictions that water and foot shortages will trigger (civil) wars and / or mass migrations. Whether it'll be the one or the other depends, I think, on how free a country is. A non-free country will have a strong police / military force that may resort to deadly violence in the case of an uprising. A truly free country will vote the regime out. Somewhere in the middle it'd be said police / military that would take over.

For my uninformed take, Iran is not a free country, the US is somewhere in the middle but I don't think an insurrection against the current regime (which has been deploying the military to mass-abduct people) would end well.