Middle-East, northern India and american Midwest. Where water-wars will be fought in the future.
There are estimates that the groundwater in the Midwest will be depleted in 20-30 years to a level that agriculture becomes impossible.
There is a worst-case Global Warming-scenario where the region around the Persion Gulf heats up drastically. Eastern-to-central Saudi-Arabia, southern-to-central Iraq and southern Iran would be so hot by 2100, they would be nigh-uninhabitable for humans.
India and China are RIGHT NOW facing off in a Cold War over the river-water flowing from the Himalaya-glaciers. A spokesperson of the indian military told journalists a few years ago that India's military is weaker than China's military, but they consider war inevitable and are preparing for a "Mutually Assured Destruction"-scenario.
https://earther.gizmodo.com/here-s-where-the-post-apocalyptic-water-wars-will-be-fo-1829793126
