The Biggest Dam in the World

CASE STUDY FOR - HARD ENGINEERING IN A LESS DEVELOPED COUNTRY

WHY AND WHEN WAS IT BUILT?

·    The Three Gorges Dam was built mainly for flood control as the Yangtze River has a history of devastating flooding, e.g. 33 000people were killed in the Hubei province in1954. China is rapidly developing and needs to find more sustainable energy sources than fossil fuels (coal) so it was also built to provide hydro-electric power.

·   Damming of the River Yangtze (the largest in China), began in 1994 and its last generator was turned on in 2012. It is currently the largest dam in the world at 2.3km long and 185m high. The huge reservoir behind is 600km long and 1km wide. According to official figures it has cost around £25 billion to build.

WHAT ARE THE POSITIVE OUTCOMES OF THE DAM?

·     Millions of people have been protected from severe flood risk

·   China the biggest burner of coal and is under pressure to reduce its greenhouse gas emissions. HEP provides 85 billion kilowatt hours of electricity, significantly reducing China’s emissions of CO₂, sulphur dioxide and coal dust.

·    Much needed jobs were created in construction and maintenance of the dam, which had a multiplier effect on the local economy.

·   Navigation has significantly improved (e.g. between Yichang and Chongqing) as larger ships can now travel from the sea much further up the river. This has reduced transport costs, traffic congestion and vehicle emissions.

·    The dam itself and its reservoir have brought in important tourist attraction e.g. during the January Spring Festival in 2012 over 500 000 tourists visited within a week, bringing in $30million in tourism-related revenues. China claims the dam has actually improved the beauty of the area.

·     The dam is seen as an important symbol of modernisation by Chinese government.

WHAT ARE THE NEGATIVE OUTCOMES OF THE DAM?

·        1300 archaeological sites and the homes of 1.3 million people were inundated by the reservoir along with their fertile farmland. Many of these people were resettled higher up the valley (e.g. to Huangtupo) but the landslides risk posed by steep slopes has forced tens of thousands to move again. The Chinese government is providing homes and compensation but many people are not happy to move to cities and have been unable to find suitable employment.

·        Hundreds of submerged mines and factories, urban growth along the reservoir and reduced velocity has seriously degraded the rivers water quality.

·        737 species of rare or endangered plants and animals live in the area affected by the river including the Siberian Crane and Baiji Dolphin. China claims that most of these species can survive higher up the slopes and that conservation measures are being put in place for the river species. However environmentalists declared the Baiji to be functionally extinct in 2007 after a 6-week survey failed to find a single individual.

·        Environmentalists argue that several smaller dams of the Yangtze tributaries would have been a more efficient and less environmentally damaging way of generating power and managing flooding

·        The dam is located in a tectonically hazardous zone with earthquakes reaching 6 on the Richter scale having been recorded here before. Dam failure could be catastrophic and cause millions of deaths.

Discussion point: Does the benefit of renewable ‘clean’ HEP outweigh the environmental damage?