2. Bangalore

Local officials in the southern Indian city have been bamboozled by the growth of new property developments following Bangalore's rise as a technological hub and are struggling to manage the city's water and sewage systems.

To make matters worse, the city's antiquated plumbing needs an urgent upheaval; a report by the national government found that the city loses over half of its drinking water to waste.

Like China, India struggles with water pollution and Bangalore is no different: an in-depth inventory of the city's lakes found that 85% had water that could only be used for irrigation and industrial cooling.

Not a single lake had suitable water for drinking or bathing.

Will Cape Town be the first city to run out of water?

3. Beijing

The World Bank classifies water scarcity as when people in a determined location receive less than 1,000 cubic metres of fresh water per person a year.

In 2014, each of the more than 20 million inhabitants of Beijing had only 145 cubic metres.

China is home to almost 20% of the world's population but has only 7% of the world's fresh water.

A Columbia University study estimates that the country's reserves declined 13% between 2000 and 2009.

• Graphene sieve makes seawater drinkable

And there's also a pollution problem. Official figures from 2015 showed that 40% of Beijing's surface water was polluted to the point of not being useful even for agriculture or industrial use.

The Chinese authorities have tried to address the problem by creating massive water diversion projects. They have also introduced educational programmes, as well as price hikes for heavy business users.

4. Cairo

Once crucial to the establishment of one of the world's greatest civilisations, the River Nile is struggling in modern times.

It is the source of 97% of Egypt's water but also the destination of increasing amounts of untreated agricultural, and residential waste.