Which is Largest Hydroelectric Dam in the World?

The world’s largest hydroelectric power generation dam lies in a prefecture level city of ‘Yichang’ in the ‘Yiling’ district in central China province of Hubei. The dam is built across the Yangtze River in the town of Sandouping.

A prefecture level city is administrative head quarter ranking below a province and above a county. The name of the dam across the Yangtze River is ‘Three Gorges Dam’ and it is the world’s largest hydroelectric power generation station as per total installed capacity. ‘Three Gorges’ is a term referring to three adjacent gorges in the middle reaches of Yangtze River.

The total installed capacity of the dam is 22,500 MW and it also serves the purpose of improving navigation as well as containing flood downstream by storing water. ‘Three Gorges Dam’ is regarded as a monument of both national as well as social importance in China; it is also weighed as a proof of China’s advancements in the field of engineering, as it uses exceptionally large turbines and is also constructed to have minimum green house gas emission.

Despite the advantages the dam has also remained controversial both in China as well as other parts of the world, as it was built flooding an archeological site and displacing approx. 1.3 million people; it is also blamed for causing ecological imbalances resulting in landslides.

Location of the ‘Three Gorges Dam’

The middle reaches of the Yangtze River has three adjacent gorges- Qutang (8 km), Wu (45 km) and Xiling (66 km). The Xiling gorge ends at Nanjin Pass in Yichang city. It is in the area of Xiling gorge where the world’s largest hydroelectric power generating dam, ‘The Three Gorges Dam’ is located. Yichang is a prefecture level city in Yiling District in the Hubei province of central China.

History – The Vision and Emergence

The ‘Three Gorges Dam’ was the brain child of the first provincial president and the founding father of Republic of China- Sun Yat-sen. As early as 1919 he envisioned that a dam across Yangtze River can be build with a production capacity of 30 million HP (22 GW) located downstream of the Three Gorges. Preliminary work for the construction of a dam on three gorges started in 1932 in the Nationalist Government led by Chiang Kai-shek.

The major breakthrough came in 1944 when an American civil engineer –John L. savage did a survey of the three gorges and prepared a project report called ‘The Yangtze River Project’. Mr. Savage was employed as head designer by the United States Reclamation Bureau, under interior ministry which oversees water resource management.

Though nearly 54 Chinese engineers went to the United States for training; the work was stopped due to Chinese Civil War in 1947.

After the formation of a communist Government in China, the chairman of the communist party of China Mao Zedong supported the Yangtze River Project but the progress was obstructed by the economical problems and the Cultural Revolution of China.

The need for a dam on Yangtze River was once again deeply felt during the Yangtze River floods of June- September 1954. Due to incessant rains the river swelled up well above its capacity and flooded the central province of Hubei; killing nearly 30000 and resulting in plague as the aftermath of floods.

The need of a dam across Yangtze River at the Three Gorges was felt by successive governments of China and was also opposed by many on the grounds of archeological destruction and causing ecological imbalances resulting in landslides. The issue was repeatedly raised and subsided with time until in 1994, when the National People’s Congress approved the construction of the dam with the approval of a 67% majority of delegates voting in the favor of construction of dam.

Construction of the dam started on December 14^th 1994. Though the dam was opened in 2003; the additional augmentation works in power plant took some time and the dam was completely functional in 2012. The shiplift was also completed in 2015 December and was functional by January 2016. Total cost incurred for the construction of the dam was 148.365 billion Yuan (approx. 21.44 billion USD).

The Ship Locks and Shiplift – A Unique Feature

We all know that the construction of a dam impounding a river hinders the movement of ships or boats across it as there is a huge difference in the water level on both sides of the dam. i.e. water level on the reservoir side is higher than that on the downstream side.

Three Gorges Dam uses two ship locks with five gates each for lifting and lowering vessels for around 20 mtrs each i.e. around 100 meters to move across the dam. The two shiplocks are installed at the two sides of the dam. The capacity of the locks is maximum 10000 tons. Ship lock consists of separated chamber filled with regulated water levels; the level of water in each chamber is maintained with pumps and inlets/outlets. The idea is to basically shift the vessel from one chamber to other with raised or depleted water level depending on whether the vessel is being shifted upstream or downstream.

Though shiplocks facilitate the transportation of large ships across the dam through narrow gorges, the process is time consuming and practically more economical and more suitable for large vessels only. For small vessels measuring up to 3000 tons the dam has installed a shiplift in 2015, for the vessels to traverse across the dam. Shiplift has many advantages like a raised shipping traffic, lower emissions and increased efficiency.

Technical Specifications (Civil & Electrical)

The Three Gorges Dam is a gravity dam made up of steel and concrete. A gravity dam uses its weight to counter balance of the hydrostatic force of water pressing against it. The dam was constructed using 27.2 X 10⁶ cubic meter of concrete and 4,63,000 tons of steel; displacing 102.6 x 10⁶  cubic meter of earth.

The dam has a total length of 2335 mtr with a height of 181 mtr. The top of the dam has a width of 40 mtrs and it is 115 meters at the base.  During the maximum reservoir level i.e. water level of 175 meters on the upstream side; the approximate length of the reservoir gets 660 km with a width of 1.12 km. Total capacity of the reservoir is 39.3 cubic km with a surface area of 1084 sq km. Total catchment area of the reservoir is 1000000 sq km.

The spillway of the dam is 483 meter long and has 22 surface sluice gates having a width of 8 meters. The spillway capacity of 1,16,000 cubic meters/second is the largest in the world.

The power plant has 32 X 700 MW (weighing 6000 tons each) main generators (Francis Type Turbines), 2 X 50 MW plant power generators making a total capacity of 22,500 MW. The main generators are installed at different locations- 14 in north side, 12 in south side and 6 in the underground plant. The annual average electricity output of the dam is 84.68 billion kWh.

World Records held by the Three Gorges Dam

Owing to its huge size and installed capacity, the Three Gorges Dam holds world records of being the first in specific areas as given below-

1) World’s Largest Water Conservancy Project.

2) World’s Largest Flood Control Project.

3) World’s Largest Hydroelectric Power Generation Plant, in terms of total installed capacity.

3) World’s Largest Concrete Dam. (Leaving behind the Grand Coulee Dam, America in 2009).

4) World’s Largest Spillway Discharge Capacity.

5) World’s Largest Displacement and Resettlement Project.

Advantages of the Three Gorges Dam

1) Economical Growth

The revenue generated from the Three Gorges Dam is so high that the complete cost of the construction of the dam was fully recovered by 2013. The project is a major source of revenue for the government of Peoples Republic of China. The annual revenue generated by the project is approx. 20 billion Yuan.

2) Low Emissions

The Three Gorges Dam reduces the consumption of nearly 30 million tons of coal preventing million tons of harmful green house gases from being produced and escaping into the atmosphere. It also saves resources which would be otherwise used for mining coal and transporting it to meet the generation requirements. The dam reduces the emission by road transport by facilitating ship navigation.

3) Flood Control

Flood control is one of the important functions of the dam. Millions reside in the cities lying downstream to the Yangtze River. The maximum reservoir capacity of 33.1 cubic km has considerably reduced the occurrence of flood in the downstream regions.

4) Water for Agriculture and Industries

The huge reservoir of the dam provides water to several industries as well as agricultural areas during the dry season. It also provides water to many industries lying in the downstream area of the river. The water level of the reservoir drops to nearly 30 meters during the dry months of December to March.

5) Improved Navigation

The dam has improved navigation of large as well as small ships resulting increased commercial activity through the Yangtze River. The dam has made the passage of ships easy and safe through the gorges by using ship locks and shiplifts. There has been a six times increase in the freight capacity of Yangtze River since the construction of Three Gorges Dam.

6) Major Tourist Attraction

The Three Gorges Dam owing to its huge size and exclusive features has been one of the most sought after tourist destinations in China with nearly around two million tourists visiting each year.

7) Downstream Project

The water from the reservoir of Three Gorges Dam also powers a 2715 MW Gezhouba Dam located few kilometers upstream from the town of Yichang.

Disadvantages of the Three Gorges Dam

1) Relocation and Submergence

Nearly 1.3 million people were relocated till 2008 with the dam completely or partially flooding 13 cities, 140 towns and 1350 villages. There also has been a reported incidence where some 13000 people never got the compensation.

2) Archeological Destruction

The construction of the dam resulted in the submergence of nearly 1300 archeological sites also altering the looks of the three gorges as the water level is raised to 90 meters. Till date the artifacts discovered are being preserved but many still lie undiscovered; submerged under water.

3) Depletion in Forest Cover and Wildlife

The construction of dam itself has resulted in the destruction of large forested area displacing 102.6 X 10⁶ cubic meter of earth. The total percent of forested area had dropped rapidly around the dam during the 1990s. Due to the governments sensibility on the issue and the importance of reforestation; the forest cover around the dam is on increase once again.

4) Depletion of Aquatic Life

The Yangtze River Basin is home to nearly 361 species of fish accounting to 27% of the total fish in China. But these fish species are now endangered and some of them have been already extinct due to the ecological disturbances caused by the construction of the dam. Many fishes are also killed by huge rotating turbine blades. Many ecologists blame the dam for the extinction of Baiji, the Chinese River Dolphin.

5) National Security

The dam is also considered as a potential target by any other world power in war with China. The anticipation of the effects of destruction of the dam would be enough to initiate a negotiation with the Chinese military or to put it on back foot.

6) Landslides

The erosion in the reservoir due to raised water level is causing landslides disturbing the surface of the reservoir. One of such incident occurred in 2009 in which around 40000 cubic meter of material plunged in to the Wu river; a tributary of Yangtze River.

FAQs about ‘The Three Gorges Dam’

Q1) Which dam houses the World’s Largest Hydro Electric Power Station?

Ans- The ‘Three Gorges Dam’ in the Central Chinese province of Hubei.

Q2) Where is the ‘Three Gorges Dam’ located?

Ans– The world’s largest hydroelectric power generation dam lies in a prefecture level city of ‘Yichang’; district ‘Yiling’ in central Chinese province of Hubei.

Q3) Across which river is the ‘Three Gorges Dam’ built?

Ans- It is built across the Yangtze River.

Q4) What kind of dam is the ‘Three Gorges Dam’?

Ans– It is a Gravity dam.

Q5) What material is the dam built from?

Ans- It is built from concrete and steel.

Q6) In which city is the dam located?

Ans– Prefecture level city of Yichang.

Q7) Name the gorge in which the area of the dam is built?

Ans-  Xiling Gorge.

Q8) Who initially conceived the idea of a dam on Yangtze River at three gorges and when?

Ans- Conceived by first provincial president and the founding father of Republic of China- Sun Yat-sen.

Q9) What was the initially estimated installed capacity of the dam?

Ans– 30 million HP (22 GW) was the initial installed capacity as proposed by Sun-Yat-sen.

Q10) In whose government was the preliminary work started and when?

Ans– It started in 1932 under the Nationalist Government led by Chiang Kai-shek.

Q11) Who did the first technical survey of the dam and when?

Ans– An American civil engineer John L. Savage in 1944.

Q12) Why was the work on the project halted during 1947?

Ans- Because of the Chinese civil war.

Q13) Which communist leader of China supported the project?

Ans– The chairman of the communist party of China Mao Zedong.

Q14) In which year the floods in Yangtze caused large scale destruction?

Ans– In 1954 resulting in 30000 deaths due to floods and its aftermaths.

Q15) Which government approved the dam’s construction and when?

Ans– National People’s Congress approved the construction of the dam in 1994.

Q16) By how much majority of delegation was the project approved?

Ans– 67% of the total delegates voted in favor of the construction of the dam.

Q17) How much was the total estimated cost of the project?

Ans– 148.365 billion Yuan (approx 21.44 billion USD).

Q18) How many people were relocated for the dam’s construction?

Ans– Nearly 1.3 million people were relocated.

Q19) How many cities/villages were submerged?

Ans– The Three Gorges Dam completely or partially flooded 13 cities, 140 towns and 1350 villages.

Q)20) How much earth was displaced for constructing the dam?

Ans– 102.6 x 10⁶ cubic meter of earth was displaced during the dam’s construction.

Q21) When was the construction started?

Ans– The construction of the dam started on 14^th December 1994.

Q22) When was the dam opened?

Ans– The dam was opened in 2003.

Q23) When was the dam completely functional?

Ans– The dam was completely functional by 2012.

Q24) When was the Shiplift installed?

Ans– The Shiplift was installed by December 2015.

Q25) How many Ship Locks does the dam has?

Ans– The Three Gorges Dam has two Ship Locks.

Q26) How many Shiplifts the dam has and what is their capacity?

Ans– One Shiplift with a capacity of 3000 tons.

Q27)  How much concrete and steel was used in building the dam?

Ans-The dam was constructed using 27.2 X 10⁶ cubic meter of concrete and 4,63,000 tons of steel.

Q28) What is the total length and height of the dam?

Ans– The total length of the dam is 2335 mtr and the height is 181 mtr.

Q29) How much is the top width and base width of the dam?

Ans– The top of the dam has a width of 40 mtrs and it is 115 meters wide at the base.

Q30) What is the maximum water level of the reservoir?

Ans– Maximum water level of the reservoir is 175 meters on the upstream side.

Q31) How much water by volume does the reservoir holds?

Ans– By volume the reservoir holds 39.3 cubic km of water.

Q32) How much is the total surface area and catchment area of the reservoir?

Ans– Total surface area of the reservoir is 1084 sq km and catchment area is 1000000 sq km.

Q33) How much is the total length and the number of gates of spillway?

Ans– The spill way is 483 meters long and has 22 sluice gates.

Q34) How much is the spillway capacity?

Ans– The spill way capacity of the dam is 1,16,000 cubic meters/second.

Q35) How many main generators does the plant have?

Ans– The dam has 32 main generators.

Q36) What is the capacity of the main generators?

Ans– The capacity of main generators is over 700 MW.

Q37) How many power generators do the plant has?

Ans– Two Power generators with 50 MW capacity each.

Q38) How much is the total installed capacity of the dam?

Ans– Total installed capacity of the Three Gorges Dam is 22,500 MW.

Q39) What is the annual average electricity output of the dam?

Ans– The annual average electricity output of the dam is 84.68 billion kWh.

Q40) What are the world records held by the ‘Three Gorges Dam’?

Ans– Following are the world records held by the Three Gorges Dam-

• World’s Largest Water Conservancy Project.
• World’s Largest Flood Control Project.
• World’s Largest Hydroelectric Power Generation Plant, in terms of total installed capacity.
• World’s Largest Concrete Dam. (Leaving behind the Grand Coulee Dam, America in 2009).
• World’s Largest Spillway Discharge Capacity.
• World’s Largest Displacement and Resettlement Project.

Q41) How much revenue is generated by the dam annually?

Ans– The dam generates annual revenue of 20 billion Yuan.

Q42) List some advantages of the Three Gorges Dam.

Ans-

• Economical growth
• Contains floods
• Water for Agriculture and Industries.
• Electricity Production.
• Improved Navigation and Water Transport.

Q43) List some disadvantages of the Three Gorges Dam.

Ans–

• Large scale displacement and submergence.
• Destruction and submergence of archeological sites.
• Depletion in forest cover.
• Depletion in species of fishes.
• Occurrence of landslides.

Q44) How many archeological sites were submerged by the dam?

Ans– Nearly 1300 archeological sites were completely submerged under water due to the dam’s construction.

Q45) The hydro project reduces the consumption of coal by what quantity?

Ans– Prevents 30 million tons of coal to be used.

Q46) What is the name of the Yangtze River dolphin now extinct?

Ans– The name of Yangtze River dolphin now extinct is- Baiji