干旱区生态环境知识资源中心

The purpose of the chapter will be to demonstrate that there area number of economic processes that have the capacity to ameliorate local water scarcity A number of and and semi-arid regions and economies encountered water scarcity in the past thirty years. Many more will encounter water scarcity in the next three decades. The analysis will review briefly a threefold synergy of ameliorating processes - first, the contribution of unaccounted water in soil profiles [known as effective rainfall to hydrologists and engineers] to the production of food staples; secondly, the global role of virtual water in ameliorating water scarcity in dry regions; and thirdly, the impact of socio-economic development on water management options. All three processes have the characteristics of being economically invisible and politically silent. But they ameliorate conflict in the easily politicised domain of water allocation and management. Their impacts are determining with respect to solving local water deficits. The role of a fourth ameliorating technology, desalination, will also be examined.

The status of the world's water resources will also be reviewed and estimates of the proportion of global water resources, which become involved in virtual water transactions will be provided. The main focus of the chapter will be on the extent to which virtual water in trade has successfully met the past and current needs of water deficit regions as part of the threefold synergy - soil water, virtual water and socio-economic development. There will be a very preliminary evaluation of the role of virtual water in meeting the future needs of water scarce regions during the demographic transition of the 21st century.

It will be shown that the water, food and trade nexus is not easy to model because of the dynamics of the political economies in the North and the South. Water sector policy-making is subject to evolving discourses, which can easily de-emphasise the underlying environmental and economic fundamentals. The chapter will conclude that invisible and silent virtual water in the invisible threefold synergy will provide the big water, that is the food-water for water scarce regions. Its invisibility and silence will, however, have the effect of attenuating the pace of water policy reform. Both reforms addressing water use efficiency and those giving consideration to the environmental services provided by water will be attenuated. A range of demographic, economic, social and political theory will be used to frame the discussion.