The Technology Context – B101

Three Gorges Dam. Worse than global warming?

Background Information

The Three Gorges Dam (TGD) spans the Yangtze River in China and is the largest hydroelectric river dam in the world. The objectives of the Dam were to help manage the flooding downstream of the site and was initially planned to provide 10% of China’s total electricity need.


There had been plans to a build a dam on the site since the early 20th Century and after many set backs the dam finally was approved by the National People’s Congress in 1992 and construction started on the 14th December 1994. Construction of the dam was scheduled to be completed by 2009 but because of delays it is now not expected to be complete until 2011.


When completed the dam will be the largest producer of hydroelectric power in the world with a reservoir that will be over 600 kilometres long and will have an average width of 1.12km. The dam will be able to produce 22,500 megawatts which is comparable to 15 nuclear power plants. (“Great Wall across the Yangtze”, n.d, para 1 – 3)


The main advantage of hydroelectric power is that it uses a free and plentiful energy source which can be scaled to suit demand and need. It also doesn’t produce any harmful by-products such as nuclear waste or any greenhouse gases from the electric energy production.

The Issue

I intend to discuss if it is better to cause a controlled devastation on a national level to help prevent the uncontrollable worldwide disaster that is global warming.


On paper hydroelectric power is the solution to the problem of finding a renewable energy source that doesn’t produce harmful greenhouse gases which may or may not be causing global warming.



However when you start to actually look at what has to be sacrificed to produce the “clean” hydroelectric energy at a comparable level to non-renewable sources such as coal then you realise that it is not a clear cut as you may initially think.


Although no greenhouse gases are produced in the making of the electricity the dam does actually produce some methane and carbon dioxide, this is from the decaying plant material in the flooded area behind the dam which in a worst case scenario can actually produce more of these gases than a fossil fuel power station. (Graham-Rowe, 2005)


The main principle behind the production of hydroelectric power is that of taking the potential energy of a large volume of dammed water and using it to rotate a water turbine and thus the generator. The force of the falling water onto the turbine is directly linked to the volume of the reservoir and the difference in height between the source and the water’s outflow; this is known as the head. The head can be increased by first running the water through a pipe known as the penstock. This is also one of the major problems with hydroelectric power as in order to produce electricity on the same commercial scale as a fossil fuel power plant a large area must be flooded to create a body of water large enough.


In the case of the Three Gorges Dam the reservoir will flood 13 cities and around 140 towns and 1,300 villages. This will cause the displacement of one and a half million people including some communities that have been settled there for many hundreds of years. The dam will also flood an estimated 1,300 known historical locations (“Great Wall across the Yangtze” n.d, para 5) some of which are of the ‘Ba’ (Kleeman 1998 pg 178) an ancient people who settled in the area 3000 years ago, and used to bury their dead in hanging coffins high up on the cliffs but these will still be flooded by the rising water levels. There are also an unknown number of undiscovered sites that will now be lost forever.


This may seem like an understandable sacrifice for the large amount of electricity that the dam will be able to produce however the dam’s production capacity may be slowly decreased because of sediment build up behind the dam. This is because the river that the dam is built upon, the Yangtze River, is the fourth largest sediment river in the world with an annual amount of 700 million tons of sediment being deposited into it. (“Great Wall across the Yangtze”, n.d, para 12) To combat this dam has an unproven design of sluice gates that should allow the sediment to pass beyond the dam and down the river. However if the sluice gates don’t work as planned then the gradual increase of sediment build up will decrease the dam’s head and thus it’s production capacity which may eventually lead to the dam not being able to produce any meaningful amount of power. There have already been studies by local Universities on how the dam (which has controlled the river flow since 2003) has affected the flow of sediment down stream, one of which has stated that the dam retains two thirds of the upstream sediment and that this retention is already shrinking the Yangtze Delta (“Three Gorges Dam shrinking Yangtze delta” n.d,) on top of which the famous city of Shanghai is built upon and it is feared that this shrinking affect may reduce the structural integrity of the very ground that Shanghai is built upon making it fall into the sea (Winchester, 1998, pg 228). This sediment retention will also affect farmers downstream of the dam as it did with the Aswan High dam in Egypt, which caused the soil quality of the land downstream too degrade so much that farmers were forced to buy expensive and potentially harmful fertilisers to allow them to get the same crop yield as they did before (“The southeastern Mediterranean ecosystem revisited: Thirty years after the construction of the Aswan High Dam”).


There are also fears that the dam may actually increase flooding downstream because of weakened riverbanks because of the lack of silt washed downstream (Yang, 2007, para 3). The backlog of sediment may also have an impact on the integrity of the dam as it did with the Banqiao Dam in which the sluice gates became blocked by sediment causing them not to be able to handle the increased water flow from an unusually large amount of rainfall causing the dam to fail. This then precipitated the failure of 62 dams in total and caused 171,000 deaths (“Hydroelectric Power – General Information” n.d, para 11).


Some have also called into the question the site of the dam as it is built on a known seismic fault which on it’s own could lead to failure of the dam and also the fact that there have been some reports which link the added weight of a dam and the reservoir behind it can cause increased seismic activity (Rozzel, 1999). This could have catastrophic effects, as if this activity were to cause the dam to fail, the release of such a large body of water would wash away millions downstream causing untold damage and destruction.


The dam will also affect local wildlife as it will separate the population of the Yangtze freshwater dolphin into two groups and will actually flood the wetland habitat of the endangered Siberian Crane which currently spends its winter in the area. There have however been some steps taken to help soften the impact of the dam such as the building of a fish ladder which will allow the migration of fish along the river. This is nothing however when compared to the Itaipu Binacional dam on the Brazil/Paraguay border. In the case of the Itaipu Binacional dam great attention was paid to the affect the dam would have on its surrounding area and because of this all the communities that were to be flooded were resettled along with their historical and cultural locations including their grave sites. A 65.000 acre nature reserve was also built to house all the animals which had been displaced; this included everything from racoons to alligators. (“Brazil and the use of Hydro Electricity”)

The Alternatives

Though the dam does have some very large negatives attached to it there aren’t many alternatives that would produce the same amount of power as the TGD. The TGD produces as much power as fifteen nuclear power plants which make it more viable on a financial level and also more practical when you consider the risks that come with nuclear power stations. A major one is the production of a highly poisonous by-product which has to be specially disposed so as not to cause a massive environmental impact. There is also the risk of a disaster such as Chernobyl or Three Mile Island, however the dam also has the risk that if it fails there are potentially millions people downstream of it that would be wiped out in the following flood. A series of smaller scale dams could also have been used instead however this would be more expensive and each would come with their own set of impacts on their local area but would have the benefit of lessening the impact if one should fail as long enough spare capacity is built into them. It would also be more manageable as the affect that each of these would of had would of been lesser than that of one big one. Also a lesser area would be flooded and perhaps some of the archaeological locations that have been flooded wouldn’t have been if smaller dams were used.


Other renewable energy sources such as wind energy are not a viable option because of their need for constant high speed winds and also their relatively low power production per turbine. Solar energy is also a non viable option due to the area’s climate.

Wider Effects the Project Has Had

The TGD has had many impacts politically with many people being firmly against the building of the dam. When final approval for the dam was being voted upon there were a record number of abstentions and dissenting votes and the dam was passed by the smallest margin in China’s history. There were also reports in the 1950’s when the dam was originally being conceived any workers that spoke out about the dam were imprisoned. There have also been stories of corruption in the modern dam as money that was sent to aid farmers who where being relocated went missing. (“Three Gorges dam money ‘missing’”)


The dam cost 180 billion Yuan to build which is a massive outlay and is indeed a limiting factor on the building of large scale dams but this cost should be recovered in ten years after the dam has become fully operationally which is currently estimated to be 2011.


Because of the scale of the TGD and the burgeoning economy of China the project has received much global coverage in the media of which a significant amount has been in a very negative light. (Three Gorges Dam is a disaster in the making, China admits) This linked with the lack of sites for other large scale dams means that the TGD may be the last large scale dam with the future lying in smaller dams and other renewable energy sources which with better technology are helping to reduce our reliance on non-renewable energy sources.

Conclusion

This brings me nicely onto whether after much research if I think that it better too cause as much devastation as the TGD has to help kerb the build up of green house gases in the atmosphere and after much deliberation I would have to say that yes I do think it is if it’s handled in the correct way. For example I think that more time should have been allocated to extensive studies on the river’s sedimentation model. This would have shown the true level of sediment flowing through the river and if it had been taken properly into account a lot of the problems the dam is currently facing wouldn’t be there or would be less significant. For example if the sluice gates had been more effectively designed the dam’s sediment retention rate might be lower which is one of the main criticisms of the project and also possibly it’s biggest impact on the balance of the river. I also think that more planning should have been provided for the relocation of not only the humans but also those of the animals and archaeological sites, an operation such as the one that took place during the building of the Itaipu Dam would have dramatically decreased the dam’s impact on the area. This operation should have also been handled centrally by a single organisation. This may have prevented some of the needed money for relocation going missing whilst going through the local governments.


However I think that the problems that the Dam has caused are nothing when compared to the possible affects of Global Warming, which may include the melting of the polar ice caps. This would result in an increase in global sea levels and flood all low lying countries which would include most of Western Europe and parts of North America. This added with the possible climates affects including more extreme weather (Intergovernmental Panel on Climate Change, 2007) would make the situation unmanageable and cause total devastation. So although the impacts of the TGD are very large they are manageable when compared to those of Global Warming and if climate change can be slowed because of projects like the TGD then the sacrifices made by the people affected and China’s historical heritage would not be in vain. So yes I do think that it is better to cause small scale devastation to help prevent or slow the impending global disaster that is Global Warming.

References

Brazil and the use of hydro electricity. Retrieved 08 January 2008 from http://predesign.wordpress.com/2007/04/09/brazil-and-the-use-of-hydro-electricity/

Duncan Graham-Rowe (2005) Hydroelectric power’s dirty secret revealed. New Scientist. Retrieved 09 January 2008 from http://www.newscientist.com/article.ns?id=dn7046

Great Wall across The Yangtze.(n.d) Retrieved 28 November 2007 from http://www.pbs.org/itvs/greatwall/dam1.html

Hydroelectric Power – General Information. Retrieved 08 January 2008 from http://www.worldofrenewables.com/page.php?pageid=48

Intergovernmental Panel on Climate Change (2007). Summary for Policymakers. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental
Panel on Climate Change. Retrieved on 11 January 2008 from http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_SPM.pdf

Lin Yang (2007) China's Three Gorges Dam Under Fire. Retrieved 8 January 2008 from http://www.time.com/time/world/article/0,8599,1671000,00.html

Ned Rozell (1999). Giant Chinese Dam May Cause Earth to Move. Retrieved 07 January 2008 from http://www.gi.alaska.edu/ScienceForum/ASF14/1465.html

Simon Winchester (1998). The River at the Centre of the World. Henry Holt & Co

Terry F. Kleeman (1998) Great Perfection: Religion and Ethnicity in a Chinese Millennial Kingdom. University of Hawaii Press

Three Gorges dam money “missing”. Retrieved 09 January 2008 from http://news.bbc.co.uk/1/hi/world/asia-pacific/6301075.stm

Three Gorges Dam is a disaster in the making, China admits. Retrieved from 01 January 2008 from http://www.timesonline.co.uk/tol/news/world/article2537279.ece

Three Gorges Dam shrinking Yangtze delta. Retrieved 07 January 2008 from http://www.physorg.com/news98971115.html

The southeastern Mediterranean ecosystem revisited: Thirty years after the construction of the Aswan High Dam. Retrieved 08 January 2008 from http://www-ocean.tamu.edu/Quarterdeck/QD3.1/Elsayed/elsayed.html