pulations, as well as to handle the wastewater and its treatment. Experience of redevelopment on this scale is limited and the closest is probably that associated with the development of the Three Gorges project in China. The uncertainty would be how the process is planned for and managed. Based on the Chinese experience initial expenditures could be anything between USD 50 billion and 100 billion. Sea level rise could also adversely affect groundwater aquifers due to increased risk from saline intrusion, especially if aquifers are being over- exploited. This could prompt the need to switch to alternative sources of water such as desalination, which at present is energy-intensive and relatively expensive. A shift in climate zones such as grain belts moving northwards and desert areas increasing in size would not just affect agricultural production and practices. It would also have an impact on urban as well as rural populations. Per capita water use is correlated with climate and to some extent increases as the climate becomes warmer. Any systemic increase in per capita water consumption would offset any gains from water demand management and leakage reduction measures. The consequence could be a need either to develop new water resources or to adopt new, more water- efficient technologies. Either way, additional investment would be required. More unstable and less predictable weather patterns will mean more droughts and more severe and frequent flooding events. One response would be to do nothing; in fact, some countries may have no option but to seek to live with the consequences as they would be constrained by natural and economic conditions in what they can do. Many countries in the Middle East, North Africa, sub-Saharan Africa and Central Asia may find themselves in this position. Water resources will already be developed and additional resources scarce and costly or beyond further development. In these cases there may have to be a reliance on temporary, unsustainable solutions, or humanitarian assistance an