The number of people in the world who live in and around cities is increasing steadily. The “State of the World Cities” report by UN- Habitat (2004) predicted that by 2030, 60 percent of the world’s population will live in cities, while the threshold of 50 percent of the world’s inhabitants living in cities was reached in 2007. Most often, this rapid urbanisation is only demographic as it is not accompanied by a similar rate of infrastructural transformation, but rather puts pressure on limited urban resources. Coincidentally, the areas of the world with the fastest-growing population already have severe water problems, and the shortages will get much worse.