Rapid expansion of urban populations presents problems for the provision of basic services to all. The rapidly growing peri-urban communities are often ignored by urban systems that may have been designed many years before the location and rate of growth was anticipated. Poor inner-city zones with high-density populations remain unplanned, with only skeletal infrastructure. In general, the rich receive these facilities and the poor do not, but the ensuing problems can affect the whole population. Particularly where squatter settlements proliferate at the outskirts of cities, a common occurrence in developing countries, access to sanitation (or drinking facilities) may be entirely lacking or inadequate. In humid zones, inadequate drainage, open sewers and broken, de-pressurized mains in urban areas can lead to the rapid transmission of water-borne diseases. Cities in arid and semi-arid regions pose another complex of environmental problems, including depletion of distant fossil water sources, aquifer pollution, and ground subsidence associated with local aquifer extraction.
The UN-mandated Water Supply and Sanitation Collaborative Council describes typical water supply and sanitation problems in expanding cities in the following way: (1) Grossly inadequate sanitation provision creates a health-threatening and offensive environment, particularly in low-income settlements; (2) Surface water sources are polluted and aquifers are depleted and degraded; (3) Excessive use of water by industry and agriculture and unsustainable consumption patterns put a sever strain on limited water resources; (4) New distant water sources are being sought and tapped at enormous cost to cater for rising demand; (5) At the same time, huge amounts of treated, potable water are wasted through leakages in distributions systems that are often old and seldom well maintained; (6) Water is delivered at a subsidized price to the middle and upper classes, while the under-served majority has an erratic, unreliable supply or depends on informal channels such as water vendors, at a much higher unit cost; (7) For a variety of reasons, many water and sanitation utilities are unable to operate and maintain existing infrastructure, to manage demand, recover service costs or make the investments that would be necessary to extend services; (8) Institutional responsibilities for water resources management are fragmented, and there is very little dialogue among the various institutions concerned.
Peru suffered a catastrophic outbreak of cholera in 1991. It started in the capital, Lima, as a result of poor water and sanitation facilities and spread rapidly over a wide area, passing out of low-income settlements across the city and into wealthy neighbourhoods. The effects on the economy were devastating. This fishing industry collapsed more or less overnight with a loss of US$ 1 billion in three months. Tourism lost $500 million over the same period. Yet the amount lost in exports and tourism alone would have been sufficient to provide a decent water supply and sanitation system for the entire population of Lima, at a cost of about $50 per household.
The 1994 plague outbreak in the Indian city of Surat (a comparatively prosperous city), which was attributed mainly to unsanitary conditions, killed 54 people, affected nearly 5,000 people, caused more than $US 1.5 billion in economic damage and triggered the exodus of 500,000 residents from Surat.
Despite all efforts of national governments, and bi- and multi-lateral agencies during the last decades, including the International Drinking Water Supply and Sanitation Decade (1981-1990), the number of urban dwellers lacking access to environmental infrastructure services in developing countries is increasing. Urban population growth is outstripping the provision of new services. In 1994 almost 280 million people in urban areas lacked access to safe water supply, while about 600 million were without adequate sanitation. Among the urban poor, less than 30% of households are connected to water supply and less than 20% have access to adequate sanitation. In addition, many people believed to be served benefited from unreliable, intermittent services providing water only part of the time.