Integrated impact quantification of proposed hydropower plants in Africa.

Among renewable energy sources, hydropower has been the most economical and well-established technology for decades. However, the construction of hydropower plants (HPPs) may have (unknown) cumulative ecological and socioeconomic ramifications in the short and long term. In Africa, 673 large HPPs are proposed. If implemented, they will alter all major river networks through dam construction and reservoir inundation, although the actual extent remains unknown. This study conducts an integrated assessment of the impacts of all proposed HPPs at both basin and continental scales. Projected reservoir areas were overlaid with spatially explicit datasets on megafauna abundance, protected areas, cropland, and human resettlement. We further calculated indices of river regulation and fragmentation, as well as potential sediment entrapment and evaporation associated with the projected reservoirs. By integrating these indicators, we identified 102 HPPs that fall within the top quarter of projects with the greatest potential overall impact. HPP capacity size alone proved to be an inadequate impact indicator, as underlined by the highest- and lowest-ranked HPPs, both of which exhibited comparably low capacities. A sensitivity analysis revealed that the ranking depends on both the number of HPPs considered and the selection of indicators included in the analysis. This study provides evidence-based information to support decision-making when balancing renewable electricity needs against the environmental and socioeconomic impacts of HPP development at basin and continental scales.