that, in Asia, about 0.54 billion out of 1.49 billion urban dwellers lived in drylands, while in Africa it is about 0.13 billion out of 0.28 billion (Balk et al., 2009). A recent assessment of water resource shortages in cities in Africa, Asia and Latin America with populations greater than100,000 estimated that, in 2000, 150 million city dwellers faced perennial water resource shortages (less than 100 litres per capita per day) within their urban extents, and this figure is projected to grow to 993 million by 2050 (McDonald et al., 2011, pp. 6312-6313). Most cities divert water from rural sources, however, and even in Africa these distances have been increasing substantially (Showers, 2002). In recognition of this, the assessment also estimated the population that would still face water shortage if the city could obtain water from within 100 kilometres. Under this measure, only 24 million faced water shortage in 2000, rising to 162 million in 2050 (McDonald et al., 2011). In these projections, urban population growth is the main driver, but climate change is a contributing factor and is growing in importance. All such estimates are highly uncertain, but they do point to what could potentially be extremely severe problems. One of the biggest urban dangers, alongside that of severe ecological and agricultural disruptions, is that water scarcity will prevent people from securing adequate water to meet their basic needs. As with coastal settlements, it needs to be recognized that not all groups will be burdened equally and that adaptation efforts that try to prevent people from living in “exposedâ€? cities could make matters worse. The water scarcity estimates above relate to water resource availability, and, in many cities, low-income residents, especially those in informal settlements, cannot secure access to improved water supplies even when local water resources are plentiful (UN-HABITAT, 2003b). Such households often lack access to the urban piped water network and depend on less reliable, less convenient, less healthy and sometimes considerably more expensive supplies. Some informal settlements are far from the piped network, while others may be refused access because they are on land that they do not own or on which residential development is not formally allowed. In some cities, there are fears that if informal settlements are provided with services such as piped water more migration and illicit settlement will be encouraged. In effect, exclusionary policies are actually helping to create the hazards, and using them to shift people away from hazards is likely to be counterproductive. Almost a third of the urban households in Africa and Asia rely on groundwater from wells in or around their homes (GrĂśnwall, Mulenga, and McGranahan, 2010). A disproportionate share of these are low-income households, who are more likely to depend on shallow wells affected by local rainfall patterns and surface water flows and to be unable to draw on distant supplies should local water resources be depleted. At the same time, there are often high levels of water being wasted by a small number of consumers and high shares of unaccounted-for water. Such conditions make it both particularly important and particularly difficult to develop more efficient urban water systems that are more equitable within urban areas, as well as between rural and urban areas. As in relation to coastal hazards, unless urban land issues are addressed, it is difficult to see how an equitable adaptation effort could be mounted. In particular, if discouraging settlement in dryland cities were to become part of an adaptation strategy, the watersupply problems faced by the most vulnerable households could be compounded. As with 32
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