Database results:
examBoard: Cambridge
examType: IGCSE
lessonTitle: Case Study: Multipurpose Dam Scheme
Multipurpose dams are massive engineering structures built across rivers to create reservoirs and serve multiple functions. Unlike single-purpose dams that might only generate electricity or control floods, multipurpose dams are designed to provide several benefits simultaneously.
Key Definitions:
Hydroelectric Power Generation: Dams convert the potential energy of stored water into electricity as water flows through turbines.
Flood Control: Reservoirs can store excess water during heavy rainfall, preventing downstream flooding.
Irrigation: Stored water can be released in a controlled manner to irrigate farmland, especially during dry seasons.
Water Supply: Reservoirs provide reliable water sources for domestic and industrial use.
Recreation: Lakes created by dams can be used for fishing, boating and tourism.
Navigation: Dams can improve river transport by creating deeper, more navigable waterways.
Aquaculture: Reservoirs can support fish farming, providing food and livelihoods.
While multipurpose dams offer numerous benefits, they also cause significant environmental changes that must be carefully considered.
• Loss of land and habitats under reservoir water
• Changes in river flow patterns
• Altered water temperature and quality
• Sediment trapped behind dam
• Reduced water flow
• Changed flooding patterns
• Erosion of riverbanks
• Disruption to fish migration
• Altered ecosystems
• Methane emissions from decomposing vegetation in reservoirs
• Reduced carbon emissions (compared to fossil fuels)
• Changes to regional climate
• Potential for international water conflicts
Dam projects don't just change the environment – they transform societies and economies too. Understanding these impacts is crucial for evaluating whether a dam project is truly beneficial.
Displacement: Large dams often force thousands or even millions of people to relocate as their homes are flooded.
Cultural Loss: Historical sites, sacred places and traditional ways of life may be lost underwater.
Health Impacts: Reservoirs can become breeding grounds for disease vectors like mosquitoes.
Improved Infrastructure: Dam projects often bring roads, schools and healthcare facilities to remote areas.
High Construction Costs: Dams require enormous initial investment.
Energy Production: Hydroelectric power provides cheap, renewable electricity.
Agricultural Benefits: Irrigation from dams can increase crop yields and food security.
Tourism Potential: Reservoirs can attract visitors and create new economic opportunities.
Reduced Flood Damage: Flood control saves money on disaster recovery.
The Three Gorges Dam on the Yangtze River is the world's largest hydroelectric dam and represents one of the most ambitious and controversial multipurpose dam projects ever undertaken.
Completed in 2012 after 18 years of construction, the Three Gorges Dam stretches 2.3 kilometres across the Yangtze River in Hubei Province, China. Standing 185 metres tall, it created a reservoir approximately 660 kilometres long – about the distance from London to Edinburgh!
Cost: Approximately $28 billion (£22 billion)
Power Capacity: 22,500 megawatts (MW) from 34 turbines
Annual Electricity: 100 billion kilowatt-hours
Reservoir Area: 1,045 square kilometres
People Relocated: 1.3 million
Flood Control: Protecting 15 million people and 1.5 million hectares of farmland from devastating Yangtze floods
Power Generation: Producing clean electricity equivalent to burning 50 million tonnes of coal annually
Navigation: Improving shipping capacity on the Yangtze River by allowing 10,000-tonne ships to reach inland ports
The Three Gorges Dam has significantly altered the Yangtze River ecosystem and surrounding environment in both positive and negative ways.
• Reduced coal burning and air pollution
• Lower carbon dioxide emissions
• Decreased risk of catastrophic floods
• Reduced need for environmentally damaging coal mining
• Loss of wildlife habitats and biodiversity
• Threatened extinction of species like the Chinese river dolphin
• Water quality issues from trapped pollutants
• Increased landslide and earthquake risks
• Sedimentation reducing dam lifespan
• Erosion of downstream riverbanks
• Changes to fish populations
• Algal blooms in the reservoir
• Methane emissions from decomposing vegetation
The Three Gorges Dam project has had profound effects on people's lives and China's economy.
The most significant social impact was the forced relocation of 1.3 million people whose homes, farms and communities were submerged by the reservoir. While the Chinese government built new towns and provided compensation, many people struggled to adapt to new environments and livelihoods. Archaeological and cultural sites dating back thousands of years were also lost beneath the waters, though some efforts were made to relocate important artifacts and monuments.
The dam generates about 2% of China's total electricity needs with renewable energy, supporting the country's industrial growth while reducing reliance on coal. Improved navigation on the Yangtze has boosted trade, with shipping costs reduced by 25-37%. The flood control function has prevented potentially devastating economic losses. However, the project's massive cost and ongoing maintenance expenses must be considered against these benefits.
The Three Gorges Dam illustrates the complex sustainability challenges of multipurpose dam schemes. While providing renewable energy and flood protection, its environmental and social costs raise important questions about whether such massive projects represent truly sustainable development. These trade-offs are common to many large dam projects worldwide.
Learning from experiences with projects like the Three Gorges Dam, experts have developed strategies to reduce negative impacts of multipurpose dam schemes:
Environmental Flow Releases: Scheduling water releases to mimic natural river flows and support ecosystems.
Fish Passages: Building structures to help fish migrate past dams.
Catchment Management: Reducing erosion and pollution in the watershed to improve reservoir water quality and reduce sedimentation.
Habitat Restoration: Creating new habitats to replace those lost to reservoirs.
Meaningful Consultation: Involving affected communities in planning and decision-making.
Fair Compensation: Ensuring displaced people receive adequate financial support and replacement housing.
Livelihood Programs: Helping affected people develop new skills and income sources.
Cultural Heritage Preservation: Documenting and relocating important cultural sites before flooding.
Multipurpose dam schemes like the Three Gorges Dam demonstrate both the potential benefits and significant challenges of large-scale water management. When evaluating such projects, it's important to consider:
As climate change increases pressure on water resources and energy systems, multipurpose dams will remain an important but controversial option for sustainable development. The lessons from existing projects can help ensure future dams maximize benefits while minimizing harm to environments and communities.
Log in to track your progress and mark lessons as complete!
Login NowDon't have an account? Sign up here.