If current consumption levels continue, by the middle of this century, mankind will be fresh out of drinking water due to population explosion.

With the world’s population expected to hit 9.6 billion by 2050, whether mankind can adapt to receding water supplies depends on whether we can develop newer technologies to find water are developed. Water shortages and severe drought are already prevalent in places like Sao Paulo, Brazil, where residents hoarding water in their apartments following a drought, and also California, which is entering its fourth year of drought.
In the 19th and early 20th centuries, whenever there was water scarcity, especially during the expansion of cities such as London and Paris, various technological solutions like expanding the network of water pipelines to pump in water other places, helped a great deal. "We can resolve our current problems if we find improved ways of desalination, for instance — removing salt from sea water to produce fresh drinking water," said Parolari.
Source-Medindia