There are many different reasons for water scarcity. Water could be scarce due to a physical shortage (physical water scarcity), or it could be , scarce because of institutional failures or the lack of adequate infrastructure to ensure a regular supply, even in places where water is abundant (economic water scarcity).

Over the last century, water use has grown at more than twice the rate of population increase globally, and it is still increasing in all sectors. The effects of climate change will intensify the risk of droughts as well. Over 2 billion people live in countries experiencing high water stress today and the numbers will continue to increase.