Hydropower Reservoir and Sedimentation : A Study of Nam Ngum Reservoir

Abstract

Hydropower accounts for approximately one fifth of the world’s electricity supply and is the best renewable energy source to meet the energy consumption of the world. With ever increasing energy demands hydropower-related construction is on the increase all over the world. Although the energy production from hydropower is efficient and cheap, the social and environmental cost can be high, with downstream ecosystem impacts caused by water quality, hydrological and sediment flux changes. In the Mekong region, the most prominent impacts follow from sediment retention by hy-dropower reservoirs. Using mathematical models to simulate generation, transport and fate of sediments provides fundamental information for assessing environmental impacts caused by hydropower development. The Nam Ngum reservoir in Lao PDR was chosen as a case area for assessing quantitatively different processes and their impacts on sediment amounts. Sediment generation, sediment transport mechanism, downstream changes in total suspended solids concentration, sediment fluxes and seasonal flow and sediment concentration variation in the case area are described in this thesis. The result shows that the amount of sediment produced in the catchment area and reser-voir have an impact on sediment fluxes. The changes in downstream sediment fluxes can cause increased erosion and morphological changes and can profoundly affect ecosystem productivity and food security. The study results can be applied for hydropower reservoir construction, for sediment management and for mitigating downstream impacts.