[Large dams, health and nutrition in Africa: beyond the controversy]

The population in sub-Saharan Africa is growing faster than increases in food production, resulting in a net decrease in food production per capita. The Food and Agriculture Organization has stated that there is a "risk of widespread hunger" which could be prevented by "effective planning of water resources". However, the potential effects of such schemes on the human population are often inadequately assessed and the effect of large dams on human health is not clear. The potential risk to human health of water resources was emphasized a few years ago but no effective preventive programs were implemented, probably because of inadequate availability of information and lack of awareness. The effects on health of "large" water resource projects are not uniform within a population. Decision-makers have tended to focus on the positive effects, to obtain support for their plans. These include: 1) improvement in the well-being of the population (safe water more readily available, new infrastructure, better access to health care) and 2) increases in the food supply (more vegetables and fish available due to irrigation). Thus, there has been a logical expectation that more, better quality food will become available as a result of these schemes, whereas in fact, health and nutrition has often worsened, particularly in young children. Most of the diseases associated with water resource management are communicable, including diseases directly related to the presence of large quantities of water, such as: malaria, which increases in incidence immediately after the building of the dam, after which a new balance develops between the human population and the parasites, schistosomiasis, the disease which increases most in response to the building of dams, particularly in its most severe gastrointestinal form, diarrhea, as water is a major means of dissemination for many organisms, including those causing digestive tract infections and gastroenteritis (amebiasis, salmonellosis, cholera), due to poor sanitation, other parasitic infections, such as onchocerciasis and trypanosomiasis, which should be monitored as they may also threaten the population. Other communicable diseases may appear or increase in incidence with the influx of migrants to the irrigated area. Sexually-transmitted diseases and HIV infection are a particular problem. The large numbers of insects (mosquitoes, blackflies) may also have harmful effects on populations adapting to the new environment. These effects are related to each other and to the environmental changes. New types of food affect people's feeding habits and generate new sources of income. However, they may also lead to new and higher expenditure. There are also likely to be major socio-demographic changes associated with changes in reproductive behavior and women's activities. The location and nature of new homes and infrastructure (e.g. schools, health centers, roads) also contribute to the success or failure of the dam project. There are many constraints to be considered and a more comprehensive approach to the problem is required. Health and nutritional status may be used as simple indicators of the ability of the population to adapt to a new environment. This makes it possible to construct a causal model to identify the most effective and relevant areas of intervention. Health and nutrition issues are of vital importance and scientific findings should be used in decision-making processes for planning future large dam schemes.