Cape Town is in the unenviable situation of being the first major city in the modern era to face the threat of running out of drinking water.
However, the plight of the drought-hit South African city is just one extreme example of a problem that experts have long been warning about - water scarcity.
Despite covering about 70% of the Earth's surface, water, especially drinking water, is not as plentiful as one might think. Only 3% of it is fresh.
Over one billion people lack access to water and another 2.7 billion find it scarce for at least one month of the year. A 2014 survey of the world's 500 largest cities estimates that one in four are in a situation of "water stress"
According to UN-endorsed projections, global demand for fresh water will exceed supply by 40% in 2030, thanks to a combination of climate change, human action and population growth.
Read more: BBC