Sedimentation supports life-cycle CH4 production and accumulation in a river valley reservoir: A hierarchical Bayesian modeling approach

Qi Li; Zhe Li; Yuanyuan Zhang; Xinghua Wu; Liu Yang; Lunhui Lu; Yongbo Chen

doi:10.1016/j.watres.2022.118861

Sedimentation supports life-cycle CH₄ production and accumulation in a river valley reservoir: A hierarchical Bayesian modeling approach

Water Res. 2022 Aug 15:222:118861. doi: 10.1016/j.watres.2022.118861. Epub 2022 Jul 12.

Authors

Qi Li¹, Zhe Li², Yuanyuan Zhang³, Xinghua Wu⁴, Liu Yang³, Lunhui Lu³, Yongbo Chen⁴

Affiliations

¹ CAS Key Lab of Reservoir Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; College of Resources and Environment, Chongqing School, University of Chinese Academy of Sciences, Chongqing 400714, China; College of River and Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074, China.
² CAS Key Lab of Reservoir Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; College of Resources and Environment, Chongqing School, University of Chinese Academy of Sciences, Chongqing 400714, China. Electronic address: lizhe@cigit.ac.cn.
³ CAS Key Lab of Reservoir Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; College of Resources and Environment, Chongqing School, University of Chinese Academy of Sciences, Chongqing 400714, China.
⁴ China Three Gorges Corporation, Wuhan, Hubei 430010, China.

PMID: 35878522
DOI: 10.1016/j.watres.2022.118861

Abstract

Reservoirs have been recognized as a source of methane (CH₄). With the gradual increase in the number of the world's reservoirs, predicting the long-term variation of reservoir CH₄ emissions is important to understand the global change in carbon cycling due to reservoir creation and operation. Here, we first categorized the origins and transport of organic carbon (OC) by reservoir creation and operation into the following four aspects: a) the decomposition of flooded organic matter, b) the sedimentation of OC from upstream sediment inputs, c) the transition of the aquatic ecosystem from lotic to lentic type, stimulating the production of autochthonous OC; and d) reservoir as the collector of anthropogenic OC inputs from surrounding communities. It was assumed that OC from the four aspects jointly determined the production and accumulation of reservoir CH₄ concentration, supporting life-cycle reservoir CH₄ emissions. A hierarchical Bayesian model of reservoir CH₄ concentration was established and calibrated by observed monthly datasets in 2018 in the Xiangjiaba Reservoir (XJB), a river valley dammed reservoir in the upper Yangtze River, China. The model explained the relative contributions of the four aspects to reservoir CH₄ production and accumulation. Approximately 78% of the CH₄ concentration was contributed by the decomposition of flooded organic matter during the first 10 years after impoundment. However, the contribution of flooding faded away after 10 years of impoundment. With the increase in reservoir age, sedimentation of OC dominantly determined the reservoir CH₄ production and accumulation. Scenario analysis of the XJB's life cycle demostrated that the CH₄ concentration in the XJB would reach its peak approximately 70 - 80 years after impoundment. In the cascade system, the upstream reservoir will help to reduce sediment OC input, and to mitigate downstream reservoir CH₄ production and accumulation. Our effort provided a new modeling approach for long-term management strategies to reduce reservoir CH₄ emissions under global change.

Keywords: Cascade reservoirs; Life cycle; Methane; Organic carbon; Scenario analysis.

MeSH terms

Animals
Bayes Theorem
Carbon / analysis
Carbon Dioxide
Ecosystem*
Life Cycle Stages
Methane / analysis
Rivers*

Substances

Carbon Dioxide
Carbon
Methane