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

Mahmoud Saber Kenawi, Fabian Vakhidi, Richard Hedger, Mobina Keymasi, Elene Gotsiridze, Knut Alfredsen, Brett Sandercock, Hanna Silvennoinen, Tor Bakken

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.