Assessing the Net Climate Impact of Norwegian Reservoirs: Integrating Land Use Change and G-res Modeling

This study evaluates the net climate impact of Norwegian reservoirs using land use change mapping, literature-based GHG flux aggregation, and G-res modeling. High-resolution historical aerial imagery and deep learning reconstructed pre-impoundment land cover, explicitly identifying wetlands previously absent from national datasets. The framework quantifies changes in CO₂ and CH₄ fluxes and cumulative GWP₁₀₀ across 52 reservoirs. Wetlands made up 20% of pre-flooded land and strongly influenced carbon dynamics. Boreal wetland fluxes produced net emissions of 342 ± 40 g CO₂-eq m⁻² yr⁻¹, driven mainly by CH₄ despite notable CO₂ sequestration. GWP₁₀₀ values ranged from -260 to 217 kt CO₂-eq, showing high spatial variability linked to pre-flood soil and land cover. Hydropower GHG intensity averaged 0.19 g CO₂-eq kWh⁻¹, lower than global estimates due to low productivity and rapid water turnover. Future research should improve soil classification, expand boreal flux datasets, and develop process-based models for pre- and post-impoundment carbon dynamics.