2003年-世界发展银行全球_Good_Dams_and_Bad_Dams___Environmental_Criteria_for_Site_Selection_of_Hydroelectric_Projects_29页_933kb

Good Dams and Bad Dams: Environmental Criteria for Site Selection of Hydroelectric Projects

Core Content

This working paper by the World Bank discusses the environmental and social impacts of hydroelectric dams and proposes a methodology for selecting sites that minimize these impacts. The report emphasizes that not all large dams are equally damaging, and that site selection is the most critical factor in ensuring environmental sustainability.

Main Points

• Hydroelectric dams vary in environmental impact: Some dams are relatively benign, while others cause major environmental and social damage. The paper distinguishes between "good dams" and "bad dams" based on their environmental consequences.

• Environmental impact is site-dependent: The severity of environmental damage from a hydroelectric project is largely determined by the location of the dam. Dams on upper tributaries are generally more environmentally benign than those on large river main stems.

• Key environmental impacts include:

  • Flooding of natural habitats: Large reservoirs can lead to the loss of terrestrial habitats, which are often more valuable than aquatic ones for biodiversity conservation.
  • Loss of terrestrial wildlife: Animals may drown or fail to adapt to new habitats, leading to high mortality rates.
  • Involuntary displacement: Dams often displace communities, especially vulnerable ethnic minorities, and can lead to environmental degradation through land conversion.
  • Water quality deterioration: Stagnant reservoirs can reduce oxygen levels and increase pollution, affecting aquatic life and human health.
  • Downriver hydrological changes: Dams alter river flow, leading to erosion, saltwater intrusion, and loss of aquatic species.
  • Water-related diseases: Stagnant water can promote disease vectors like mosquitoes and snails, increasing the risk of diseases such as malaria and schistosomiasis.
  • Impact on fish and aquatic life: Dams block fish migration, alter flow patterns, and degrade water quality, harming aquatic ecosystems.
  • Floating aquatic vegetation: Eutrophic reservoirs can lead to rapid growth of weeds, affecting navigation, water quality, and infrastructure.
  • Loss of cultural property: Reservoirs can submerge archaeological, historical, and religious sites.
  • Reservoir sedimentation: Sediment buildup reduces the efficiency of power generation and can affect water quality.
  • Greenhouse gas emissions: Flooding forests and other biomass can release significant amounts of carbon dioxide and methane, contributing to climate change.

• Mitigation options are available but not always effective:

  • Establishing compensatory protected areas.
  • Resettlement programs for displaced communities.
  • Pollution control measures.
  • Managing water releases to mimic natural flow patterns.
  • Fish passage facilities and hatcheries.
  • Selective forest clearing before reservoir filling.
  • Physical or chemical control of aquatic weeds.
  • Salvaging cultural property and storing it in museums.
  • Watershed management to reduce sedimentation.

• Good site selection is the most effective mitigation strategy: The paper argues that selecting sites with smaller reservoirs and minimal environmental impact is the best way to prevent or reduce negative effects. It also highlights that many problematic dams are best left undeveloped.

Key Information

• Project size matters: Dams with smaller reservoir surface areas relative to power generation are more environmentally and socially desirable.
• Environmental criteria should guide planning: Energy planners must consider environmental impacts when selecting dam sites, and prioritize projects that minimize harm.
• Complementary civil works contribute to environmental damage: Access roads, transmission lines, and quarries can cause additional deforestation and habitat loss.
• The World Bank's Natural Habitats Policy: The paper aligns with this policy, which discourages the conversion or degradation of critical natural habitats that cannot be adequately compensated.
• The report is part of the LCR Sustainable Development Working Paper Series: It aims to share best practices and analytical insights on sustainable development in the Latin America and Caribbean region.

Conclusion

This report provides a robust framework for evaluating hydroelectric dam sites based on environmental and social criteria. It underscores the importance of site selection in reducing the negative impacts of dams and recommends that energy planners integrate environmental considerations into their decision-making processes. While mitigation measures can help address some issues, they are not always sufficient, and the best approach remains choosing sites that minimize environmental harm from the outset.

Tables Summary

• Table 1: Lists the adverse environmental impacts of hydroelectric projects and corresponding mitigation options. The table highlights that good site selection is the most critical factor in minimizing these impacts. It includes:
  • Impacts of the dam and reservoir (e.g., flooding, wildlife loss, water quality issues).
  • Impacts of complementary civil works (e.g., access roads, quarries).
  • Mitigation strategies such as protected area establishment, resettlement assistance, water quality management, and fish passage facilities.

Acknowledgments

The paper acknowledges the contributions of Doug Mason, who compiled data on Latin American hydroelectric projects, and several World Bank staff members who provided feedback and support. It also recognizes the input from experts such as Dominique Egre, Gaitan Guertin, Jose Goldemberg, and Paul Dulin.

Foreword

The report is part of the World Bank's efforts to promote sustainable development in the Latin America and Caribbean region. It emphasizes the need for environmentally and socially responsible dam development and aligns with the broader goals of the World Commission on Dams and other international initiatives. The findings are the authors' own and should not be attributed to the World Bank.