Investigation of Benefits and Problems Associated With Dams as a Multi-Purpose Scheme

Multi-purpose schemes can be defined as the water management schemes that provide multiple benefits to the surrounding area. The Three Gorges dam in China is one such example. The dam is located on the Yangtze river which runs east through China to the East China Sea. The Three Gorges project involved a series of smaller dams and one very large dam with a large reservoir to store water behind it.

The dam has provided China with many benefits. The dam is the largest renewable energy source in the world producing 8.4 billion kilowatt hours in 2010. This has aided the Chinese governments in the development of inland China which lags behind the more developed coastal regions.

The reservoir created by the dam has also provided the region with water for agriculture. And because the reservoir is so large it has increased the humidity in the area providing the farmers with more consistent rainfall for their crops. The construction of the dam has also created many jobs for locals and helped to improve the standard of living in the area.

The dam has also widened many shipping routes in the area creating business and economic development in the Yiling area as it creates an availability of cheap labor and trade avenues. It also allows for the flood and drought control of the river.

Despite the benefits of the creation of the dam and the resulting reservoir, they have also led to some major drawbacks. The loss of velocity in the river has allowed for the proliferation of schistosomiasis parasite which used to be controlled be seasonal flooding and the fast flowing stream. The area of largely still water behind the dam has now be contaminated by the snails so now the water is not usable to humans as contact can cause fevers, joint pain and persistent diarrhoea.

The dam has also led to an increased frequency and severity of landslides in the area as the constant raising and lowering of the dams water levels has led to the surrounding soil to become loose due to vary levels of water pressure making it very prone to landslides. The reservoir has also led to unpredictable seismic activity know as reservoir-induced seismic activity. The reservoir sits on two major active fault lines, the Jiuwanxi and the Zigui–Badong. Altering the water pressure has been said the strain the faults resulting in 822 recorded tremors in the span of seven months.

The dams has also led to reduced sediment downstream and increased deposition along the river. The dams have trapped huge amounts of sediment behind them causing there to be a reduced amount of sediment in the river which be have caused the shrinking of the Yangtze delta. The decreased velocity of the river has also meant that what sediment is left too heavy to be carried by the river which has led to increased deposition in the river channel blocking trade channels the dam was supposed to enable.

The land slides and earthquakes combined with the large amounts of land lost to flooding has caused the about 1.4 million people to be displaced. An estimated 10 billion (40% of the Three gorges budget) has been used to relocate these people but many have complained about not receiving any of the promised 4000 dollars per head from the government. The large amounts of flooded land has also impacted the wildlife in the area. A lot of precious habitat has been lost to the water and more are being lost to deforestation as the dam spurs economic development in the area. Species such as the Chinese sturgeon and the baiji dolphin some that are found no where else in the world are in peril as the dam decreases flooding and lowers the water level which disrupts the series of lakes where these fish reside.

The decreased flow has also caused sea water to creep in near the mouth which has caused an explosion of jellyfish population which threaten local fish species by feeing on their eggs and larvae. The dam has also caused droughts lower downstream in Shanghai at the mouth of the Yangtze because of a reduction in freshwater flow down the Yangtze. An unnamed official has claimed that the dam has resulted in a 50% reduction in flow. The large reservoir has also increased evaporation so there might just less water in the channel.

Overall, I disagree with the statement that Multi-Purpose dams provide more benefits than problems. Dams drastically change the surrounding ecosystem and can cause more problems than we could possibly anticipate. This combined with the drastic relocation of people makes them highly impactful on the surroundings while providing very little benefit. River ecosystems are very delicate and disrupting this balance on such a populous river can be disastrous.