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Securing water for citiesPosted: 31 Jan 2007
Some 60 per cent of all freshwater withdrawn for human use ends up in urban areas - either directly for use in factories and for drinking and sanitation, or indirectly through the consumption of irrigated crops.
Many urban centres have outgrown their capacity to provide adequate freshwater supplies for their needs. Many have tapped all the nearby surface water sources, and groundwater resources are being drawn upon faster than the natural rate of recharge. Problems of water shortage can be especially acute during periods of low-rainfall.
There are often problems with water quality too. The rivers or lakes on which cities draw are frequently of poor quality. Sometimes they are saline because of return water from irrigation, or contaminated with agricultural chemical and human and livestock wastes. They may also be heavily polluted by industries or by other users 'upstream'. Groundwater may also be contaminated, especially if industries have been dumping their wastes down deep wells.
In many coastal cities, local aquifers have been over-pumped, resulting in saltwater intrusion.
Here are some basic facts on Water from the UN-Habitat State of the World's Cities Report 2001:
- City dwellers in Africa only use 50 litres of water per person per day. The highest median price of water is also highest in Africa.
- Less than 20 per cent of households in Africa are connected to piped water and only 40 per cent have access to water within 200 metres of their house.
- In industrialised countries, almost 100 per cent of households are connected to piped water. The average water consumption for these households is 215 litres per person daily.
- In many cities in developing countries, 50 per cent or more of water is lost as a result of leaks and poor management.
- Less than 35 per cent of cities in the developing world have their wastewater treated.
Desludging latrine pits in Kibera, Nairobi.
© IRC/Madeleen Wegelin
Problems of water scarcity are particularly acute in arid areas. Hundreds of urban centres in relatively dry areas have grown beyond the point where adequate supplies can be tapped from local or even regional sources.
Coastal cities in Peru (including Lima), La Rioja and Catamarca in Argentina and various cities in Northern Mexico are among the many which are finding it difficult to expand freshwater supplies. Many urban centres in Africa's dryland areas face particularly serious problems because of a combination of rapid growth in demand for water and unusually low rainfall in recent years.
One example is Dakar, Senegal,where water supplies have to be drawn from ever-more distant sources. The local groundwater supplies are fully used (and polluted) and local aquifers over-pumped. A big proportion of the city's water has to be brought in from the Lac de Guiers, 200 km away.
But for most urban centres facing water shortages, this is more the result of inadequate investment and poor water management than a lack of fresh water resources (see section on Environment and Health in Cities).
State of the World's Cities Report 2001.
Water and Sanitation in the World's Cities, UN-Habitat, 2003.