Water for people.pdf - WHO Thailand Digital Repository

1 7 6 / C H A L L E N G E S T O L I F E A N D W E L L - B E I N GCities: Competing Needs in an Urban Environmentnumber relying on interbasin transfers (Showers, 2002), even thoughprovision for water in most of them is still very inadequate.Nations with very limited rainfall such as Algeria have had tomake very large investments in dams and interbasin transfers. In1962, Algeria had ten dams supplying 480 million cubic metres (Mm 3 )a year, by 2002, it had forty-eight dams supplying nearly 2.8 billionm 3 a year. Despite this, most cities in Algeria suffer problems ofinadequate and irregular supplies, in part linked to much-belowaveragerainfall in recent years.Contamination from wastewater dischargesThe contamination of rivers, lakes, seashores and coastal waters isan example both of the impact of city-generated wastes on thewider region and of governments’ negligence in controlling pollutionand managing surface and wastewater flows. This often leads toserious health problems for large numbers of people whose watersupply is drawn from these water sources. In cities on or close tocoasts, untreated sewage and industrial effluents often flow intothe sea with little or no provision to pipe them far enough out tosea to protect the beaches and inshore waters, thereby posing amajor health risk to bathers.The possibilities for improvement vary greatly. In Europe andNorth America, great improvements have been made in reducingwater pollution, mostly through stricter controls on industrialdischarges and more sophisticated and comprehensive treatment ofsewage and stormwater. In most cities in low- and middle-incomenations, the problems are not so easily addressed as they havemuch more serious non-point sources of water pollution because ofthe lack of sewers and drains in many city districts and peripheralareas. Additionally, many uncollected wastes are washed intostreams, rivers and lakes.Liquid wastes from city activities often have far-reachingenvironmental impacts. It is common for river and coastal fisheries tobe damaged or destroyed by liquid effluents from city-based industrieswith significant numbers of people losing their livelihood as a result.River pollution of this sort can lead to serious health problems insettlements downstream (see for instance CSE, 1999), and the sourcemay become unusable for agriculture downstream.Cities and water-related natural disastersThe most common form of disaster associated with water is flooding,which is generally linked to storms or periods of unusually highrainfall and, for coastal cities, exceptionally high tides and stormsurges (for more information on risk management, see chapter 11).However, while most floods arise from natural causes, most ofthe deaths, injuries and loss of property they cause in cities are theresult of inadequate attention given to flood warning, floodpreparation and post-disaster response. The ways in which citiesdevelop can exacerbate risk from floods – or lessen them. In wellgovernedcities, flooding risks can be minimized through not onlyprovision and maintenance of drains but also good watershedmanagement (to limit the volume of flood waters and the speedwith which they build up) and land use control (for instance to limitthe exposure of soils during construction of new developments).Many cities also use recreational water bodies, parks and otheropen spaces to provide flood storage. Among high-income cities atrisk of flooding, it is now common for detailed, sophisticated floodriskmaps to have been developed. These maps make each localauthority aware of the risk within their jurisdiction and help identifyoptimum investment patterns to limit risk (see the Greater Tokyocase study, chapter 22). However, as noted earlier, in poorlygoverned cities, large population concentrations frequently developin locations that are known to be at high risk of flooding. To thehazards inherent in the site are added those linked to a lack ofinvestment in infrastructure and services, especially drainage, andlittle or no watershed management. It is also common for suchsettlements to combine high densities, shelters built with flammablematerials and widespread use of open fires and kerosenestoves/lamps which mean high risks of accidental fires with, usually,little provision for effective firefighting and emergency treatment forthose who are burnt.However, even with careful management, urbanization canincrease the consequences of floods. For instance, in Japan, rapidurbanization over the last fifty years has concentrated more peoplein flood-prone areas; today close to half the population and threequarters of the property value are located within the flood-proneareas of rivers. While flood mitigation measures have decreased theoccurrence of major rivers overflowing their banks and ofembankment failures, reducing both the severity and the area offlood damage, the increased concentration of people and highvalueproperty in floodplains have increased the costs of flooddamage. Meanwhile, river basins that are being rapidly urbanizedare losing their natural water-retaining and water-retardingfunctions – as can be seen again in the Tokyo case study.Cities’ ecological footprintsThe extent of the environmental changes caused by any city on itssurroundings and the size of the affected area is much influencedby the city’s size and wealth, as well as the nature of its productionbase and of the resource endowments of the region around it. It isalso significantly influenced by the quality of environmentalmanagement both within the city and in the surrounding region.Although much of the literature on the generation and transferof environmental costs from cities concentrates on the surroundingregion, the demands made by larger and wealthier cities for food,fuel and raw materials may be increasingly met by imports from