Three Gorges Dam: friend or foe of riverine greenhouse gases?

Whole system thinking subverted the conventional perception that dams would enhance GHGs emission in a large river. Dams are often regarded as greenhouse gas (GHG) emitters. However, our study indicated that the world's largest dam, the Three Gorges Dam (TGD), has caused significant drops in annual average emissions of CO2, CH4 and N2O over 4300 km along the Yangtze River, accompanied by remarkable reductions in the annual export of CO2 (79%), CH4 (50%) and N2O (9%) to the sea. Since the commencement of its operation in 2003, the TGD has altered the carbonate equilibrium in the reservoir area, enhanced methanogenesis in the upstream, and restrained methanogenesis and denitrification via modifying anoxic habitats through long-distance scouring in the downstream. These findings suggest that 'large-dam effects' are far beyond our previous understanding spatiotemporally, which highlights the fundamental importance of whole-system budgeting of GHGs under the profound impacts of huge dams.

Automated summary

This study finds that the Three Gorges Dam has significantly reduced greenhouse gas emissions along the Yangtze River, leading to a decrease in CO2, CH4, and N2O emissions and a reduction in emissions to the sea. These findings highlight the importance of whole-system budgeting of greenhouse gases under the influence of large dams.