dams

I will now present my opening arguments. C1) Damming requires the inundation of original landscapes. After a dam is built, the resulting reservoir - typically a valley or water inlet - will have to be inundated. This creates a plethora of problems and negative impacts, which I will demonstrate below. SC1) Inundation of settlementsDamming often inundates settlements, which incurs high costs of resettlement, including compensation. Moreover, farmers whose agricultural land were flooded will lose their livelihoods unless the government allocates a new piece of farmland to them, which adds to the cost. Original industrial areas may be flooded as well. Social unrest may result of the original residents are unhappy with the compensation. For example, dams along the Lancang (Mekong) River resettled a number of peasants, including 4000 who were resettled to Aihua to make way for the Dachaoshan dam. The government had to spend US$3.3 million on an irrigation scheme in Aihua, but water shortage still occured there, and the soil became barren and unproductive. The contrast with their old village is stark: Back then, they could eat for two years with one harvest. Some villagers have even resorted to continuous protests. (1) Given the plight of the resettled villagers and the huge costs incurred in relocation, there is no reason to build a dam. SC2) Inundation of natural landscapesThe inundation of natural landscapes is another deleterious effect of dam-building. The original aquatic ecosystem will be damaged to make way for our reservoir. The water will be acidified and polluted, Moreover, the surrounding terrestrial ecosystem will be destroyed altogether. This reduces biodiversity, destroys habitats of animals and plants, and threatens the ecological equilibrium. There are also environmental side effects such as the release of methane when trees decompose after inundation and the spread of waterborne diseases. For example, a dam in Colombia damaged the habitats of birds. (2) The Balbina dam in Brazil destroyed 1400 sqaure miles of rainforest and trees rotted in the water, while acidification of water killed off aquatic life. (3)SC3) Inundation of historical sitesRiversides are often hailed as the cradles of ancient civilisation. There is often a wealth of historical and cultural relics to be found along the riverbanks. However, dam construction inundates these sites. The most notorious example is the Sanxia Dam in China. It inundated rock suites with prehistoric fossils, hundreds of paleolithic and neolithic sites, and sites belonging to the ancient Ba tribe (said to be the ancestors of the Tujia). As for the more recent sites, a handful of sites with high touristic value - Shibaohai, Zhang Fei Temple, Fengdu Ghost Town and Baiheliang - were relocated, but the remainder, including hundreds of Ming and Qing Dynasty buildings and a large number of ancient canals, disappeared under the water forever. Among these was the Fengjie port, discovered in 2003, which was the setting of an extremely famous Tang Dynasty poem. The port was flooded soon after its discovery. (4)C2) Risk of dam collapseDam collapse is a huge risk with devastating consequences. There are numerous possible causes of this. The dam may collapse during an earthquake, hurricane or other serious natural disaster. The dam may become a target in war. The dam may simply be unable resist the water pressure after heavy, persistent rain. Whatever the cause, dam collapse will cause widespread flooding, and threaten human life and property. For example, in 1975, Typhoon Nina destroyed 62 dams in Zhumadian, China, and killed 171,000 people. (5) The Johnstown flood flattened the entire town and killed over 2200. (6)C3) Damming modifies the microclimateDam creation can modify the microclimate of the affected area. There are several ways in which this happens. Firstly, the large body of water increases evaporation, cloud formation and precipitation. Secondly, as water has low albedo, it is good at storing heat. This will lead to a 'hot tub effect' which results in a drastic increase in potential (and, coupled with the original increase in water storage, actual) evaporation rate, as well as heat balance. A hotter, wetter climate is thus created. For example, the Itaipu Dam in Brazil led to a 4°C increase and was the likely cause of a 30% decrease in crop yields. If the situation continues, they may have to adapt and plant crops more suited to the new microclimate, such as cassava or sugar cane. (7)C4) Dams may trigger earthquakesA lesser-known impact of dam construction is their earthquake-triggering tendency. As the resulting reservoir alters the amount of pressure exerted onto the lithosphere below, reservoir building may result in rock displacement along faults. Increased infiltration and percolation caused by the increase in water storage will also lead to a decrease in shear stress, which facilitates rock displacement. There have been over 100 cases of reservoir-induced seismicity (RIS). Even the 2008 Sichuan earthquake, which killed 80,000, may have been caused by the Zipingpu Dam's construction. (8)C5) Downstream impacts of dammingDownstream impacts of damming include reduced floods in the lower course, which is harmful to floodplains that rely on annual floods to maintain the fertility of its alluvial soils. Moreover, in drier years, the blocking the flow of water to the lower course will induce drought there. This will lead to a host of negative impacts, including crop failure due to the lack of irrigation water and subsequently a drop in food suppply. Increased deposition will also result from the lower river discharge, leading to silting. If the upper and lower courses are located at different countries, this will even threaten international relations. For example, in 2011, the Chinese government admitted that the Sanxia (Three Gorges) Dam had led to serious droughts in the lower course. Three million hectares of farmland were devastated, and millions experienced a lack of clean drinking water. Ships were stranded and the survival of the endangered Yangtze finless porpoise was at risk. (9) Laos' decision to build a dam along Mekong River triggered vehement opposition from neighbours, including Cambodia, Thailand and Vietnam. (10)R1) Lake-side resortsI understand my opponent's position on the effects of dam construction on tourism. However, it must be duly noted that the inundation of natural landscapes and cultural relics because of dam construction will lead to a drastic drop in ecotourism and cultural tourism. The disappearance of ancient historical sites and diverse flora and fauna will only undermine the touristic value of flooded sites. R2) Provide clean drinking waterI do not deny that reservoirs can stabilise clean water supplies. However, as I have shown above, the dam will cause droughts downstream, which reduces water supplies there. (1) . https://www.chinadialogue.net...(2) . http://www.ecosystemmarketplace.com...(3) . http://www.tropical-rainforest-animals.com...(4) . http://www.sulanteach.net... (5) . http://www.eeo.com.cn... (6) . http://abcnews.go.com... (7) . http://www.internationalrivers.org... (8) . http://www.internationalrivers.org... (9) . http://www.nature.com... (10) . http://www.voanews.com...