Dams might solve water shortages, but bad design can cause pollution and disease.
Engineers and designers must adopt a new approach to the planning of dams and irrigation systems in developing countries if outbreaks of disease and social and environmental disasters are to be stemmed.
This is the conclusion of Dams and disease - ecological design and health impacts of large dams, canals and irrigation systems,* a new book by US ecologist William Jobin. He urges the World Health Organisation to 'creatively join' the World Bank - responsible for funding the majority of such projects - and 'promote the healthy development of tropical water resources'.
It is true that the world is facing a global water crisis. Population growth, increasing consumption and global warming mean that once fertile areas will soon become arid desert.
Reservoirs have long been seen as an effective way of dealing with water shortages. By holding up the flow of rivers communities can use the water for drinking, washing and crop irrigation and generate power at the same time.
The Chinese Three Gorges Dam across the Yangtse river is set to be the largest dam in the world. Costing £15bn and taking decades to build, the 88m high dam will create an enormous reservoir and provide 18GW of power for central China.
It will provide a stable source of water for the region and avoid the need to build new, but highly polluting, coal fired power stations.
But Jobin points out that the dam comes with potential environmental and social problems. Three Gorges will displace around 1M people and destroy the ecology of three vast valleys. Precise environmental impacts are hard to estimate but the resulting reservoir will engulf many factories lining the Yangtse, creating a risk of severe pollution problems.
However, beyond the headline environmental impact of such schemes, Jobin points out that the potentially disastrous effect on health is often missed and often not even calculated.
'Water resources have been developed in ways which cause disease and other social and environmental problems,' he explains. 'After engineers have carelessly designed and constructed many of these water projects, other people responsible for the health, social and environmental sectors have had to implement remedial measures at great expense.'
Jobin's book says that often reservoirs create breeding grounds for bacteria, insects and parasites. Good reservoir design can make it harder for these to survive by eliminating sheltered shorelines to stop swampy areas forming.
Canals and drainage systems can also be designed to encourage water to flow quickly and avoid ponding. Schemes in areas with a high risk of disease should also come with suitable local health care facilities.
Malaria, diarrhoeal diseases, malnutrition, Salmonellosis, Hepatitis, Bilharzia, river blindness and Hookworm are just some of the main water- associated killers identified as being commonly associated with dams in the developing world.
'Balancing ecological needs with the demands of industries and urban centres is largely a contest between powerful political forces and the mute but fundamental needs for sustaining life on our planet,' argues Jobin.
Reorganising WHO's involvement in project design and giving other United Nations agencies greater roles is the key to implementing improved designs. 'The unsatisfactory situation is getting worse,' says Jobin. 'But it doesn't have to be that way.'
*Published by E&FN Spon, 11 New Fetter Lane, London EC4P 4EE. Price £60.