Carbon footprints of pre-impoundment clearance on reservoir flooded area in China's large hydro-projects: Implications for GHG emissions reduction in the hydropower industry

Abstract

Pre-impoundment clearance in an area to be flooded by a reservoir is a commonly applied engineering measure to remove vegetation cover, buildings, structures and solid waste landfill as a clean production approach in the hydropower industry. By removing forests and trees, pre-impoundment clearance is also among one of the most applicable and practical measures to significantly minimize the potential increase in greenhouse gas (GHG) emissions after reservoir impoundment. By using Economic Input-Output Life Cycle Assessment (EIO-LCA) method and following ISO 14067, the present study evaluated carbon footprints of pre-impoundment clearance in China's five largest hydro-projects: the Three Gorges Dam Project (TGD), the Xiangjiaba Project, the Xiluodu Project, the Baihetan Project, and the Wudongde Project, and discussed the trade-offs between these carbon footprints and the contributions to GHG emission reductions from pre-impoundment clearance. The carbon footprints of pre-impoundment clearance in these hydro-projects ranged from 0.020 gCO2eq·kWh−1 to 0.434 gCO2eq·kWh−1; the TGD project had the maximum carbon footprint among the hydro-projects. Removal of buildings, structures, and solid wastes created the largest share (over 95%) of carbon footprints of pre-impoundment clearance. Removal of forests and trees in pre-impoundment clearance could possibly reduce potential GHG emissions after reservoir impoundment, which equal to approximately 14.43%–246.80% of pre-impoundment clearance. Higher anthropogenic activity in terms of population density in reservoir areas to be flooded and smaller hydro-project energy density resulted in higher carbon footprints from pre-impoundment clearance. In China's cases, pre-impoundment clearance is concluded to be a significant measure of GHG emission reduction in hydropower industry.