Dirty water is the world's greatest single killer. Every day it claims the lives of 25,000 children. Every year about four million children under five die from just one water-borne disease, diarrhoea. That is the equivalent of wiping out every pre-school child in Britain and Australia one year, killing under fives in Canada and Germany over the next 12 months, and so on, year after year.
In rural Africa children are commonly ill, largely from waterborne diseases, for 140 days in the year. Even those who survive may be gravely damaged, for repeated illness causes malnutrition, stunting their physical and mental growth.
And not just children suffer. At any one time half the inhabitants of developing countries are ill with diseases associated with dirty water and poor sanitation. Four-fifths of all illness - and a third of all deaths - are caused this way, while an average person in the Third World loses one tenth of his or her productive time each year to waterborne diseases. India forgoes 73 million working days each year - and $600 million in health costs and lost production - to the effects of dirty water.
Hundreds of millions of people in the rural Third World go through life without ever using a tap. In rich countries, we each use between 150 and 1,000 litres of water a day. Relatively prosperous Third World city dwellers use between 100 and 350 litres, while poorer neighbours depending on public hydrants may manage on 20 to 70. But, in the city slums or, above all, in the countryside, where there are few taps, the amount drops dramatically; in rural Kenya, for example, it can fall as low as two to five litres a day, close to the limit for bare biological survival.
Every drop of the scarce, often dirty water has to be carried, inevitably by women, often for miles and hours on end. A typical full container weighs 20kg, the same as a suitcase at the limit allowed by most airlines. In parts of Africa and India women often have to walk for at least six hours just to get to and from the waterholes, and queue for another four hours when they get there.
This task dominates their day, denying them the chance to do more productive work. The weight of the water causes backache, and can result in disability.
Once brought, every drop is treated like gold. When a UN official chided an African villager for not making her children wash their hands after defecating (a practice which cuts the incidence of diarrhoea almost in half) she retorted: "I have to carry our water seven miles a day. If I caught anyone wasting water by washing their hands, I would kill them."
The 1980s, by international decree, was designated the International Drinking Water and Sanitation Decade with the avowed goal of providing everyone alive with clean water by 1990. It did not achieve this target, the deadline was moved to the year 2000, and no-one expects this to be met either. Nevertheless, the World Health Organisation reports the drive did bring safe water to over a billion people for the first time. In almost every country, it says, the proportion of people with clean water increased, sometimes dramatically. In Burkino Faso it went from 30 to 68 per cent.
The benefits are enormous. In economic terms, the Venezuelan Government found that every dollar invested in clean water paid for itself five times over in increased production. The human gains are incalculable. And, morally, the state of its water remains a crucial yardstick of the world's values.