No water, no sanitation, avoidable ill-health: the hallmarks of the unplanned urban settlement. For the first time there are now more urban than rural dwellers. Such a massive population shift, making capitals like Mumbai, Lagos and Dakha bigger than all but Tokyo, is one of the greatest challenges for governments of developing countries.
But while providing water infrastructure even in planned urban environments is both complex and expensive, in the unofficial shanty towns that fringe many of the world's developing cities, the problems are vast. Bangladesh, for example, would need to connect around 65,000 homes every month between now and 2015 to bring water to 99% of all its urban dwellers including those in slums.
Developing countries cannot afford the capital costs of providing water and sanitation in the face of such rapid urban expansion. Slums will always be at the back of the queue. For improved and extended infrastructure, foreign aid is essential.
Yet despite widespread anxiety about achieving the millennium development goal for water and sanitation provision, there are reports that even where money is available, it has not been spent.
Part of the explanation is that aid sometimes comes with conditions the country cannot or does not want to meet. A scheme in Malawi, for example, was delayed for years as government and then Malawians themselves campaigned against the type of private sector involvement being demanded.
But increasingly there are success stories. Mozambique has a tripartite arrangement between public and private sectors, involving an asset-holding company for the infrastructure, an independent regulator and a private sector asset manager.
Involving the private sector while holding down the cost to consumers who see water both as a right (as the UN accepts) and as something that is freely available every time it rains. Changing attitudes is a necessary first step.
"It is a myth that people can't afford to pay for water," says John Kandulu, WaterAid's policy director for southern Africa. "But it takes education and communication, the assurance that they are paying the right price."
Increasingly, the small-scale provider is recognised as a valuable partner in bringing water to slums and shanties. Some water vendors buy and resell water legally. However, others steal water from official supplies with illegal pipes that are frequently contaminated by waste.
To make a system of small business-supplied water work effectively, it needs regulation to ensure the quality of water and the fairness of the charges. The most effective way of securing and sustaining water supplies, regulation and service improvements is an empowered local community.
