Those slum-dwellers who buy their water by the litre, whether they live in Kibera, Dharavi or a Brazilian favela, will pay more for it than their neighbours in richer districts who get it from a tap.

• 那些贫民窟里的居民买水总是以升计量，在肯尼亚的贫民区基贝拉，孟买的贫民区达拉维，以及巴西的贫民窟，水价都比富裕城区水龙头里流出的水贵好多。