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

Jinren Ni; Haizhen Wang; Tao Ma; Rong Huang; Philippe Ciais; Zhe Li; Yao Yue; Jinfeng Chen; Bin Li; Yuchun Wang; Maosheng Zheng; Ting Wang; Alistair G L Borthwick

doi:10.1093/nsr/nwac013

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

Natl Sci Rev. 2022 Jan 28;9(6):nwac013. doi: 10.1093/nsr/nwac013. eCollection 2022 Jun.

Authors

Jinren Ni¹, Haizhen Wang¹, Tao Ma¹, Rong Huang¹, Philippe Ciais², Zhe Li³, Yao Yue⁴, Jinfeng Chen¹, Bin Li¹, Yuchun Wang⁵, Maosheng Zheng⁶, Ting Wang¹, Alistair G L Borthwick⁷

Affiliations

¹ Key Laboratory for Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
² Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre Simon Laplace, Commissariat à l'Énergie Atomique et aux Ènergies Alternatives, CNRS, Université de Versailles Saint-Quentin-en-Yvelines, Gif-sur-Yvette 91191, France.
³ Key Laboratory of Reservoir Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
⁴ State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China.
⁵ Department of Water Environment, China Institute of Water Resources and Hydropower Research, Beijing 100038, China.
⁶ MOE Key Laboratory of Regional Energy Systems Optimization, Resources and Environmental Research Academy, North China Electric Power University, Beijing 102206, China.
⁷ School of Engineering, The University of Edinburgh, Edinburgh EH9 3JL, UK.

Abstract

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.

Keywords: Three Gorges Dam; Yangtze River; equilibrium; greenhouse gas; spatiotemporal variation; whole system analysis.