70% of the world's surface is covered with water, yet..
Southeastern US towns are now officially out of water - Orne, TN, for example.
The US SW especially Phoenix, is sucking eons old aquifers dry and when that deep, deep hole gurgles its last, people will be leaving Phoenix in droves. No water, no city.
They will truck it in, they will sell or distribute bottled water, which has to be trucked in, and that costs money. There is no big pipe they can use to transport water from say, Lake Mead to Phoenix. It doesn't exist. And this is in the world's richest country!
Southern Saharan states like Sudan - of which Darfur is a part - have been in a drought for decades, yet the overall population of Africa continues to rise. 900 million I heard today from the lips of Paul Martin the former PM of Canada.
Wars over water, oil, land, food - all over the world have their roots in poverty. When the poor get hungry or thirsty they get desperate and will become refugees or stand and fight. Fight or flight, it's what all animals do. Some governments prefer to sell them arms to fight their wars rather than sell them the technology to solve the problems. If the money spent of guns in north Africa from Somalia to Dakar had been spent on desalination plants say, nobody would be going thirsty. There would be irrigation. There would be food.
If Georgia and Tennessee had spent the money on water supplies they had spent on NASCAR and buying bigger trucks there would be no water shortage.
Still, water shortages and poverty are ultimately about population. Too many people fighting over finite resources. The problems will not stop until people stop making babies - and we all know how well that program is going to work, but if people don't stop reproducing at the rate that has produced 5 Billion people in 150 years, nature will do it for them.