Perspectives and challenges for desalination in the 21st century*2

Abstract While the importance of desalination has been increasing steadily over the past decades, views on the merits of desalination among water professionals differ. Some portray desalination as a panacea for much of the world's water woes. Others perceive desalination very negatively because of its alleged high costs, energy intensity and environmental impacts. While none of these extreme positions appears to be justified, it remains even more necessary to gain an objective understanding of the real stakes in desalination in the context of integrated water resources management. The World Bank has undertaken a regional study that aims at improving the understanding of desalination within the Bank and among some of its clients in the Middle East, North Africa and Central Asia. It also tries to clarify the conditions under which desalination can help in reaching the United Nation's Millennium Development Goals (MDGs) for water supply and sanitation. The study, which has been funded by the Bank-Netherlands Water Partnership, includes case studies of Algeria, Cyprus, Jordan, Malta, Tunisia and Uzbekistan. A key conclusion of the study is that desalination alone cannot deliver the promise of improved water supply. The ability to make the best use of desalination is subject to a series of wider water sector related conditions. In some countries weak water utilities, politically determined low tariffs, high water losses and poor sector policies mean that desalinated water, just like any other new source of bulk water, may not be used wisely or that plants are at risk of falling into disrepair. Under these conditions, there is a risk that substantial amounts of money are going to be used inefficiently, and that desalination cannot deliver its promise to alleviate water scarcity and to contribute to the achievement of the MDGs. It may be preferable not to engage on desalination on a large scale unless the underlying weaknesses of the water sector are being seriously addressed. A program to address these weaknesses should include a reduction of non-revenue water; appropriate cost recovery; limited use of targeted subsidies; sound investment planning; integrated water resources management; proper environmental impact assessments; and capacity building in desalination as well as in water resources management and utility management. In any case, desalination should remain the last resort, and should only be applied after having carefully considered cheaper alternatives in terms of supply and demand management. A second conclusion is that the private sector can play a useful and important role in funding and operating desalination plants, but only if the above conditions are met. If these conditions are absent, there is a risk that excessive investments in desalination become a drain to the national budget, either directly under public financing or indirectly through implicit or explicit guarantees under private financing. A third conclusion is that desalination technology itself has evolved substantially, making it significantly cheaper, more reliable, less energy-intensive and more environmentally friendly than it was a few decades ago. This is especially true for reverse osmosis, which is gaining a large share of the market outside the Gulf countries which continue to use mainly distillation technologies.