Reservoirs are significant sources of atmospheric greenhouse gas (GHG) emissions, partially counteracting the carbon sink effect of terrestrial ecosystems. However, due to the high temporal and spatial variability of GHG fluxes in reservoirs, emission estimates remain highly uncertain. Traditional approaches, which primarily rely on field measurements and empirical formulas, often suffer from low resolution and fail to comprehensively capture the spatiotemporal variations in reservoir carbon emissions. Therefore, developing a high-resolution, dynamic model for simulating reservoir GHG emissions is essential for improving estimation accuracy. This study developed and integrated a Carbon Greenhouse Gas (C-GHG) module (including CO₂ and CH₄) into the Environmental Fluid Dynamics Code (EFDC). This module simulates the spatiotemporal variations of CO₂ and CH₄ in reservoirs while comprehensively accounting for key physical and biogeochemical processes governing their production, transport, and emission. To evaluate its performance, the study applied the model to a typical reservoir in southwestern China, simulating the dynamics of CO₂ and CH₄ emissions and assessing their global warming potential.
Figure 1 CO2 and CH4 processes involved in model development
The results demonstrate that the model effectively captures the dynamic variations of CO₂ and CH₄ at different monitoring points throughout the year and accurately represents their spatiotemporal distribution patterns. The study reveals that tributary regions, particularly shallow areas, serve as hotspots for C-GHG emissions. Seasonally, the reservoir functions as a CO₂ source during autumn and winter but may act as a CO₂ sink in spring and summer. In contrast, CH₄ remains a net emitter year-round. Over a 100-year timescale, CH₄ accounts for 81.5% of the reservoir’s total global warming potential (GWP), with CH₄ ebullition contributing 66.5% of total CH₄ emissions. Overall, the model developed in this study provides a robust tool for quantitatively assessing the spatiotemporal dynamics of reservoir C-GHG emissions and underscores the critical role of CH₄ ebullition in tributary regions. These findings suggest that current global estimates of reservoir GHG emissions may be significantly underestimated.
Figure 2 Spatiotemporal variations of CO2 flux in each season
Figure 3 Spatiotemporal variations of CH4 flux in each season
The research has been published in Journal of Hydrology as the paper “Estimating CO2 and CH4 fluxes from reservoirs: Model development and site-level study”. Weiwei Shi is the first author of this paper, with Prof. Zhifeng Yan as the corresponding author. This work was supported by the National Natural Science Foundation of China and the National Key R&D Program.
Figure 4 GWP contribution over the entire year and from each season
Weiwei Shi, Wenxin Wu, Hongxiang Fan*, Qingqing Sun, Xueqi Niu, Shilu Wang, Si-liang Li, Shengkang Liang, Zhifeng Yan*. Estimating CO2 and CH4 fluxes from reservoirs: Model development and site-level study. Journal of Hydrology, 2025: 132794. Link：https://doi.org/10.1016/j.jhydrol.2025.132794
