Abstract:

The greenhouse effect has become an important global climate issue, and inland waters are an important source of emissions of the greenhouse gases (GHG) CO₂ and CH₄. It has been found that hydropower energy, once considered clean, may cause an increase in CO₂ and CH₄ emissions from river waters as a result of damming and impounding water. In order to actively respond to the national “Dual-Carbon” goal and clarify the impact of damming and impounding on GHG emissions from water bodies, the G-res Tool, a model for evaluating the net flux of GHG emissions from reservoirs, was used to simulate the CO₂ and CH₄ emission fluxes before and after impoundment of 10 completed terrace reservoirs on the main stream of the Lancang River. The average annual GHG (CO₂ and CH₄) emission flux of the 10 reservoirs after impoundment is 162.81 g CO₂e/(m²·a), which is much lower than the global average level of reservoirs, but all of them behave as “sources” of GHGs, with an overall upward trend from upstream to downstream. Emissions are dominated by CO₂, with an annual CO₂ emission fluxes 36 times that of CH₄, which is dominated by diffuse and off-gas emissions. After considering the GHG emissions prior to reservoir impoundment and the impacts of unrelated anthropogenic sources, the average annual net flux of GHG (CO₂ and CH₄) emissions from the reservoir is 225.70 g CO₂e/(m²·a), suggesting that damming increases the release of GHGs from the reservoir waters. However, hydropower is still a relatively clean energy compared to thermal power generation.

Key words: Lancang River, Terraced power station, Reservoir greenhouse gas, Model, Net emission flux