Dams are planned, constructed, and operated to meet human needs - generation of energy, irrigated agricultural production, flood control, public and industrial supply, supply of drinking water, and various other purposes. Dams impound water in reservoirs during times of high flood that can be used for human requirements during times with inadequate natural flows. Positive impacts of dams are improved flood control, improved welfare resulting from new access to irrigation and drinking water. Without dams there would be insufficient food to feed the worlds people and energy would be generated by burning fossil fuels that produce greenhouse gases. Despite this progress there remain significant concerns about the environmental impacts of dams. These environmental impacts are complex and far reaching, remote of the dam, and may occur in time with the dam construction or later and may lead to a loss of biodiversity and of productivity of natural resources. This bulletin compiles improvements in knowledge and state of the art technology to avoid or mitigate environmental impacts of dams on the natural ecosystem as well as to the people that depend upon them for their livelihood and also addresses the mitigation of environmental impacts on dams and reservoirs.
Les barrages sont planifiés, construits et exploités de maničre ą répondre aux besoins humains. Les barrages retiennent l'eau dans les réservoirs pendant les périodes de forte crue, une eau qui peut źtre utilisée pour les besoins de l'homme pendant les périodes dinsuffisance des débits naturels. Les impacts positifs de barrages sont le contrōle des crues et l'amélioration du bien-źtre résultant du nouvel accčs ą l'irrigation et ą l'eau potable. Sans barrages, la production alimentaire serait insuffisante pour nourrir la population du globe et l'énergie serait générée en brūlant des combustibles fossiles qui produisent des gaz ą effet de serre. Malgré ces progrčs, d'importantes préoccupations subsistent quant aux retombées des barrages sur lenvironnement. Les impacts environnementaux sont complexes et dune grande portée. Ils peuvent se produire au moment de la construction du barrage ou plus tard et peuvent entraīner une perte de la biodiversité et de la productivité des ressources naturelles. Le présent bulletin compile l'amélioration des connaissances et des technologies les plus récentes pour éviter ou atténuer les impacts environnementaux des barrages sur l'écosystčme naturel ainsi que pour les personnes qui en dépendent pour leur subsistance. Il aborde également l'atténuation des impacts environnementaux sur les barrages et les réservoirs.
1. INTRODUCTION;
2. RESERVOIR WATER QUALITY;
3. MANAGEMENT OF THE IMPACT OF HYDRAULIC PROCESSES;
4. DOWNSTREAM IMPACTS OF LARGE DAMS;
The Commission Internationale des Grands Barrages (CIGB) / International Commission on Large Dams (ICOLD) is a non-governmental International Organization which provides a forum for the exchange of knowledge and experience in dam engineering. The Organization leads the profession in ensuring that dams are built safely, efficiently, economically, and without detrimental effects on the environment. Its original aim was to encourage advances in the planning, design, construction, operation, and maintenance of large dams and their associated civil works, by collecting and disseminating relevant information and by studying related technical questions. Since the late sixties, focus was put on subjects of current concern such as dam safety, monitoring of performance, reanalysis of older dams and spillways, effects of ageing and environmental impact. More recently, new subjects include cost studies at the planning and construction stages, harnessing international rivers, information for the public at large, and financing.
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