Unclean water is an “immeasurably greater threat to human security than violent conflict” across the developing world, says the latest annual report from the United Nations Development Programme.

The report says, “‘Not having access to clean water' is a euphemism for profound deprivation. It means that people walk more than one kilometre to the nearest source of clean water for drinking, that they collect water from drains, ditches or streams that might be infected with pathogens and bacteria that can cause severe illness and death.”

Each year 1.8 million children die from diarrhoea that could be prevented; 443 million school …