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Health impacts of large dams

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Abstract

Large dams have been criticized because of their negative environmental and social impacts. Public health interest largely has focused on vector-borne diseases, such as schistosomiasis, associated with reservoirs and irrigation projects. Large dams also influence health through changes in water and food security, increases in communicable diseases, and the social disruption caused by construction and involuntary resettlement. Communities living in close proximity to large dams often do not benefit from water transfer and electricity generation revenues. A comprehensive health component is required in environmental and social impact assessments for large dam projects.

Introduction

The environmental, social, and health consequences of large dam projects are receiving increasing international attention (Baviskar and Singh 1994, McCully 1996; IUCN and World Bank 1997). Although dams are important for water and energy supply, flood management, and irrigation, millions of people, mostly in less-developed countries, are exposed to their adverse health and social impacts Goldsmith and Hildyard 1984, Hunter et al. 1982, Scudder 1997a. In the industrialized world, river developments such as those on the Mississippi and Rhine have resulted in substantial ecosystem damage. During the last 10 years, more than 40 million people have been resettled involuntarily due to large dam projects (World Bank 1996). If completed, the Three Gorges Dam in China will require the relocation of more than 1 million people. Water projects have resulted in vector-borne diseases, loss of food security, pollution, and social problems that negatively influence health Goodland 1995, Hunter et al. 1982, Hunter et al. 1993, Scudder 1997a. Large dams provide cogent examples of the impact of large-scale infrastructure and development on health Cooper-Weil et al. 1990, Hughes and Hunter 1970. They also are a paradigm for globalization in poorer countries, hence generating debate on equitable resource allocation.

Globalization, or the liberalization of world commerce, has caused much suffering, as vast amounts of physical and human resources have been transferred from less-developed to industrialized countries Benatar 1998, Shafaedin 1995. At best, the benefits of globalization are distributed unevenly and economic growth often occurs at the expense of the poorest countries and communities (Soros 1998). In the case of large dams, the benefits of hydropower and water usually are transferred long distances from the project site, to cities and industrial areas. Benefits to local populations may be limited to the provision of roads and temporary employment. Those living in a large dam catchment areas can be left worse off than they were prior to construction. About two-thirds of all large dams are being built in less-developed countries and, because the private sector is playing an increasing role, water and electrification for surrounding communities are not regarded as priorities.

The Lesotho Highlands Water Project (LHWP), currently one of the five largest dam projects globally, is an example. The first phase of the LHWP, costing over US $2.4 billion, will provide water to the heavily populated Gauteng Province of South Africa and ensure Lesotho’s self-sufficiency in electricity. Approximately 7,000 people have been employed in construction, to a limited extent compensating for the loss in labor remittances from the decline of the South African mining industry. Dam and tunnel work in the poorest districts of Lesotho has brought the benefits of roads and infrastructure, employment, and some direct funding of rural development and poverty alleviation (LHDA 1996). The long-term revenue stream of water royalty payments has been allocated to national development projects.

Section snippets

Health Issues

Large dams influence health at not only the reservoir site but also upstream, downstream, and at national or even regional levels (Table 1). Increases in the prevalence of schistosomiasis, malaria, encephalitis, hemorrhagic fevers, gastroenteritis, intestinal parasites, and filariasis (including onchocerciasis and bancroftosis) have been documented after dam and irrigation projects. Although not dealt with in this paper, large dams also influence the health of animals through increases in

Macroeconomic Impacts

The relationship between health status and macroeconomic factors is complex, and often it is difficult to measure the health benefits of economic growth in developing countries Sen 1994, WHO 1993. The LHWP has raised Lesotho’s gross domestic product, a macroeconomic factor that directly influences health indicators such as infant mortality. As the gap between mean household income and the poverty line in Lesotho is small, many families have been aided in that the LHWP is large enough to protect

Resettlement, Compensation, and Development

Involuntary resettlement remains one of the most serious outcomes of large dam projects (Table 2). Those forced from their homes by construction and inundation often are ignored; it is assumed that they somehow will benefit from the dam. There are numerous cases where dam resettlement has been carried out under the threat of violence and little, if any, compensation was provided. Resettled families lose homes, land, food sources, and employment, and they are exposed to social dislocation

Conclusions

Large dams demonstrate the interaction between public health and large-scale engineering projects. Although development generally has positive health impacts, the link between project expenditure and improved health is indirect and often tenuous. Roads and construction activity bring benefits, but generally, improvements in water supply, employment, and agriculture are short-lived, and their termination can have catastrophic consequences. Dams often are justified as essential for “flood

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