Evaluating the Feedback of the Reservoir Methane Cycle to Climate Warming under Hydrological Uncertainty

Abstract

Freshwater reservoirs are widely recognized as methane (CH4) emission hotspots. Existing research has shown that temperature and hydrological conditions significantly affect wetland CH4 cycling processes. However, the feedback of the CH4 cycle to climate warming remains unclear for deep reservoirs where seasonal water thermal stratification exists. This study combined a reservoir CH4 cycling model and a Statistical DownScaling Model (SDSM) to evaluate reservoir CH4 cycling feedbacks under multiple climate change scenarios while accounting for hydrological uncertainty. Daily air temperatures in 2100 were predicted by the combination of the CanESM5 model and a SDSM. To address hydrological uncertainty, we selected three representative hydrological years (i.e., wet, normal, and dry) to create hydrological scenarios. Results showed that annual sediment CH4 production increased with warming, ranging 323.1–413.7 × 103 t C year−1 among multiple scenarios. Meanwhile, the CH4 oxidation percentage decreased with warming, which meant warming promoted sediment CH4 release non-linearly; 67.8–84.6% of sediment ebullient flux was ultimately emitted to the atmosphere (51.3–137.7 × 103 t C year−1), which showed ebullition was the dominant emission pathway. Higher air temperatures and drier conditions generally promote reservoir emissions. This study is helpful for predicting reservoir emissions while directing decision-making for reservoir sustainability.

Impact of Reservoir Operation Policies on Spatiotemporal Dynamics of Sediment Methane Production and Release in a Large Reservoir

“…As expected, it is found external environmental conditions affect reservoir CH 4 emissions for the case study reservoir, and additional work might be needed for further exploration. For example, Li et al (2023) evaluated the impact of climate warming by linking a reservoir model with a climate prediction model. Future studies may explore the long-term influence of operation policies, while accounting for changes in climate, reservoir inflow, and pollution loading conditions (Battin et al, 2023;Giuliani et al, 2021).…”

“…For example, Li et al. (2023) evaluated the impact of climate warming by linking a reservoir model with a climate prediction model. Future studies may explore the long‐term influence of operation policies, while accounting for changes in climate, reservoir inflow, and pollution loading conditions (Battin et al., 2023; Giuliani et al., 2021).…”