|Title:||Modelling greenhouse gas emissions from the Three Gorges Dam|
|Subject:||Hong Kong Polytechnic University -- Dissertations.|
Greenhouse gases -- China -- Yangtze River Gorges.
Dams -- China -- Yangtze River Gorges.
Hydraulic engineering -- China -- Yangtze River Gorges.
|Department:||Department of Civil and Structural Engineering|
|Pages:||viii, 71 leaves : ill. (some col.) ; 30 cm.|
|Abstract:||The project of The Three Gorges Dam is one of the most important projects in China. However, it is controversial and there are debates over the costs and benefits. The purpose of this study is to examine one of the environmental issues of this project which is green house gas (carbon dioxide CO2 and methane CH4) emissions of the related area. The concerned area is a small section of the entire extend (660 km) of the reservoir which covers 15 km in length along the reservoir to the Three Gorges Dam. After the dam is built, a large area will be flooded. Because of this, it will affect the CO2 and CH4 emissions from the reservoir due to increased amount of biomass under water. In this study, gas emissions of CO2 and CH4 are calculated. In order to carry out the calculations, it requires knowing the flooding area which is calculated from Landsat images by using ArcGIS software and terrain models of the concerned area are built. The estimation of flooded areas is done by calculating polygons area covering the water body and the river bed. Subsequently, the slope area, which represents the flooded area, is calculated. Before the impoundment (years before 2003), the flooded area for the concerned region is about 10 km2. After that, in year 2008, the flooded area is estimated for about 25 km2. The gas fluxes in the study area are obtained from other literatures since there is no on-site measurement is made. The results shows that the small section of the Three Gorges Dam reservoir produces about 40 kilotons of CO2 per year and about 2 kilotons of CH4 per year after impoundment. The amounts of production of CO2 and CH4 after the filling of water are 40 times and 20 times more respectively comparing to that before. Also, a model is built to demonstrate the possible trend of the CO2 and CH4 produced after the dam is operated for 30 years. It shows that the emission of CO2 decreases continuously while the emission of CH4 also decreases comparatively slower over the same period.|
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