Case Study Of The Three Gorges Dam

The following case study on the Three Gorges Dam illustrates the pros and cons of concrete gravity dam construction and is an excellent complement to the material discussed in the technical paper.

China’s Three Gorges Dam (TGD) is the largest power generating plant in the world. The TGD is a hydroelectric concrete gravity dam that spans the Yangtze River, in Hubei province.5 It is located in the Xilingxia gorge which is one of the three gorges of this river.5 Costing a total of over 30 billion US dollars 6, the TGD project was put in place for several reasons including flood protection, energy production, increased navigability throughout the Yangtze River and access to fresh water for the citizens. 3 The construction of this dam is having a major impact on China’s national economy, and its performance is critical to the large population living in Three Gorges region. 3 Upon its completion, the dam will measure 2.6 kilometres in length, 186 meters in height and it will form a 645 kilometre long reservoir in the midsection of the Yangtze. 3 The dam is designed to generate an output of 17680MW which includes 26 generators at 680 MW per unit. 3 The following figure shows the exact location of Three Gorges dam.

Figure 3: Map of the Three Gorges Dam

In terms of construction, the dam will be composed of 32 primary generators which will allow the dam to reach its maximum power output capacity. 26 generators are found on the dam itself while the remaining are built below a neighbouring mountain.6. Furthermore, a ship lift capable of vertically transporting ships (weighing as much as 3000 tons) from one water level to another will be built on the north side of the Three Gorges Dam.6. Other than the ship lift, a series of locks have been installed designed for boats weighing up to 10 000 tons; approximately four hours are needed for transit of these vessels. 6. The ship lifts and locks constructed as part of the TGD are very beneficial aspects as they promote increased navigability throughout the Yangtze River. By transporting more freight on the river, a reduction in emissions caused by the trucking industry is predicted,6 which is beneficial to the environment. The following table shows a summary of several specifications of the dam:

Table 3: TGD Physical Summary (http://scholar.lib.vt.edu/theses/available/etd-12142004-125131/unrestricted/SAllin_010304.pdf)

Location

Dam Site

Sandouping, Hubei Province, China

Dam Crest

185 meters

Dam Length

2,000 meters

Reservoir Specifications

Normal Pool Level

175 meters

Flood Control Level

145 meters

Total Storage Capacity

39.3 billion cubic meters

Flood Control Storage

22.1 billion cubic meters

Power Generation

Installed Capacity

17,680 MW

Unit Capacity

26 units, 680 MW/unit

Inundation

Land

632 km-long, 19 cities, 326 towns

Arable Land

30,000 hectares

Population

1,980,000 people

As mentioned previously, prevention or mitigation of the effects of floods is one of the primary reasons for the construction of the Three Gorges Dam since Chinese records show that about one major flood per decade occurs in the area, some killing over 300 000 people. 3 The TGD which has a total of 22 billion cubic meters of capacity destined to flood control will allow China to control some major floods which also have a great impact on the economy.3 Energy production is also a major benefit involved in the construction of the dam. In fact, with its output of 18 million KW, the TGD is world’s most powerful plant. It was found that the TGD would produce a total of nearly 10% of the available energy in China.3 A third reason for the construction of the dam would be for consistent access to fresh water for consumption or agricultural use. In fact, it is known that the Yangtze River’s water level fluctuates significantly which could affect the amount of water available for use; the TGD will be able to supply this water consistently, mitigating the effects of these fluctuations in the water level of the river. 3. Finally, increased navigability in the river is another benefit related to the construction of this dam. The Three Gorges Dam allows for a direct access from the Pacific Ocean into mainland China, which in turn promotes increased trade in the cities; in the end, increased navigability will create new job, new markets will emerge, and there will be a better economic vitality in general.3 It is clear that there are significant benefits to the construction of this dam, as it will not only have a positive impact on the Chinese economy, but it will also increase the quality of life of Chinese citizens and contribute to human development.

Unfortunately, some argue that the environmental and social price to be paid with respect to the construction of the Three Gorges dam outweighs its benefits to society. In fact, the environmental impacts including effects on biodiversity, emissions, erosion and sedimentation as well as waste, and the social effect of relocation of millions of citizens causes great harm to the Chinese population.

The following information on the environmental and social effects of the construction of the Three Gorges Dam is written with the help from a report from Samuel Robert Fishleigh Allin which will be listed in the references used for this technical paper.

Environmental effects

The construction of dams definitely has a detrimental impact on the environment. Some of the impacts involved are greenhouse gas emission, loss of aquatic biodiversity, loss of water quality, loss of wildlife, and creation of wetlands. The construction of the dam negatively alters the composition of the water in the Yangtze River, already one of the most polluted rivers in the world due mainly to coal shipping. First, the dust resulting from the construction itself will enter and pollute the water. It is found that the oxygen levels as well as the temperature of the water, which affects fish downstream, are also altered upon the dam’s completion. Furthermore, greenhouse gases are released from the breakdown of vegetation and silt, which lowers the surrounding air quality. Also, a silt build-up in the river could possibly affect the reservoirs of the dams increasing the possibility of floods, upstream from the dam. The flow of silt throughout the river is very crucial to aquatic wildlife; without it in proper quantities, the organisms can be deprived of a sufficient quantity of nutrients. Moreover, the Three Gorges Dam affects the stream flow of the River and this disrupts the aquatic ecosystems which are very dependent on the timing of the water level fluctuations. Finally, one more aspect that is more related to the health and safety of the population is the fact that the TGD was built near a fault line and the magnitude and force that this dam exerts on the ground can increase the chances that an earthquake occurs.

Social effects

It is important to account for the different negative social impacts before launching the construction of a large dam. The most significant social implication related to the Three Gorges Dam is the fact that over one million people living near the reservoir area had to be relocated, many already living in severe poverty, while the compensation for relocation was often inadequate. Water from the Three Gorges Dam is expected to flood 13 cities and over 100 000 acres of farmland which really disturbs the people`s everyday life as it results in loss of jobs and well being. Some of the difficulties involved in the resettlement process include medical services, schools, drinking water and food as well as electricity. Also, another social impact is the fact that some of the archaeological sites near the dam including historical artefacts will become inaccessible due to the construction of the dam. On the other hand, one social benefit of the TGD is flood control provided by the dam will save people from disasters in the future as the frequency of a major flood is expected to be at 1 in 100 year’s frequency. To end the section on social impacts a figure of the scope of the resettlement area caused by the construction of the TGD is shown:

http://www.ctgpc.com/benefifs/images/06.jpg

In conclusion, although the construction of the Three Gorges Dam is great for the development of the Yangtze River, contributes to the Chinese economy, and presents benefits such as flood control, energy production, increased navigability and access to fresh water, it is clear that the negative social and environmental price to pay to sustain these benefits is a major cause of concern for the future.