1.10 - Dams
The global trend of increased large dam construction
The construction of large dams, defined as structures over 15 metres in height, has seen a significant rise worldwide. With completions nearing two per day, these projects are pivotal in addressing water and energy demands. Notable examples include the Akosombo Dam in Ghana, the Tucurui Dam in Brazil, the Hoover Dam in the USA, and the Kariba Dam in Zimbabwe.
Reasons for the surge in dam building
- Energy demands - Large dams generate hydroelectric power (HEP), offering a renewable energy source to meet the needs of expanding populations and industries.
- Water storage needs - Dams create reservoirs to store water for agriculture, industry, and domestic use, especially in regions prone to drought.
- Flood management - By controlling river flow, dams help mitigate the risk of devastating floods in vulnerable areas.
- Economic growth - Infrastructure projects like dams create jobs during construction and support industrial development with reliable energy and water supplies.
The purpose and scale of the Three Gorges Dam in China
Located on the Yangtze River in eastern China, the Three Gorges Dam is the largest dam in the world, stretching over 2 kilometres in length and standing more than 100 metres high. The reservoir it creates extends over 600 kilometres. This massive structure was designed to address China's escalating demands for electricity and water as the nation transitions towards a more urban, western-style lifestyle. The Yangtze River basin, home to 400 million people, produces 66% of China's rice and drains an area of 1.8 million square kilometres, discharging vast amounts of water annually.
Key features and objectives of the Three Gorges Dam
- Electricity generation - Aimed at producing substantial hydroelectric power to reduce reliance on fossil fuels like coal.
- Water management - Provides storage to support agriculture and urban needs in a densely populated region.
- Flood control - Protects millions of people living downstream from the catastrophic flooding that has historically plagued the area.
- Economic development - Supplies energy to key growth areas like Shanghai and Chongqing, fostering industrial and urban expansion.
Advantages of the Three Gorges Dam for energy, economy, and flood protection
The Three Gorges Dam offers numerous benefits, particularly in terms of energy production, economic progress, and safeguarding communities from natural disasters.
Positive impacts of the Three Gorges Dam
- Massive energy output - Capable of generating up to 18,000 megawatts of electricity, eight times more than the Aswan Dam and 50% more than the Itaipu Dam in Paraguay.
- Economic boost - Provides affordable energy to support industrial hubs, creates thousands of jobs during construction, and drives development in targeted regions like Shanghai and Chongqing.
- Flood prevention - Shields approximately 10 million people from flooding, a critical benefit given the historical loss of life due to floods in China, with over 300,000 deaths recorded in the 20th century.
- Improved navigation - Raises water levels by around 90 metres, transforming dangerous rapids into a navigable lake and enhancing shipping routes above the dam.
Disadvantages of the Three Gorges Dam on people and the environment
Despite its benefits, the Three Gorges Dam has significant drawbacks, affecting both human populations and the natural environment.
Negative impacts of the Three Gorges Dam
- Mass displacement - Around 1.2 million people were forced to relocate, with entire towns submerged under the reservoir. Resettlement areas, often at elevations above 800 metres, have colder climates, thin, infertile soils, and steep terrain, making adaptation difficult.
- Environmental concerns - Annual silt loads of about 530 million tonnes threaten to clog the reservoir, potentially silting up ports and causing coastal erosion downstream due to reduced sediment flow. Aquatic species, such as the Yangtze River Dolphin, are believed to have gone extinct due to habitat disruption.
- Geological risks - The region is prone to seismic activity and landslides, and the immense weight of water in the reservoir may increase instability, heightening the risk of natural disasters.
- Cultural losses - Valuable archaeological sites, including the Zhang Fei temple, have been lost to flooding, erasing parts of China's heritage.
- Financial burden - The project cost up to $70 billion, placing a significant economic strain on national resources.
- Limited flood control effectiveness - Many recent floods have originated from tributaries joining the Yangtze downstream of the dam, reducing its overall effectiveness in flood prevention.
Broader implications of large dam projects
The case of the Three Gorges Dam reflects wider issues and considerations surrounding the global trend of dam construction. These projects often involve complex trade-offs between development goals and social or environmental costs.
Key considerations for large dam initiatives
- Balancing benefits and costs - While dams provide energy and flood protection, they often come at the expense of displaced communities and altered ecosystems, necessitating careful planning and mitigation strategies.
- Sustainability challenges - Siltation, habitat destruction, and seismic risks highlight the need for long-term environmental assessments before construction.
- Social and ethical dilemmas - Forced relocations and loss of cultural heritage raise questions about the fairness and human impact of such projects.
- Global relevance - With dam building accelerating worldwide, lessons from projects like the Three Gorges Dam can inform future decisions, ensuring better integration of social, economic, and environmental priorities.