News Release

Unraveling the energy-emissions-ecosystem trilemma of African hydropower expansion

The expansion of hydropower is an attractive solution for many African countries striving to meet their growing energy needs. However, this might affect the alteration of riverine ecosystems and still result in substantial greenhouse gas emissions.

Peer-Reviewed Publication

Politecnico di Milano

African rivers are among the mightiest in the world, such as the longest, the Nile River, and the deepest, the Congo River. African rivers are pristine environments less fragmented and regulated by human activity than rivers in Europe and North America. For this reason, they are part of and contribute to some of the most biodiverse ecosystems in the world. At the same time, these rivers have allowed human society to thrive and flourish for thousands of years supporting the coexistence of human and natural systems. However, this delicate balance might be in peril.


Africa’s hydropower contributes between 15% and 20% of the total electricity consumed in the continent representing the largest renewable power source, around 10 times as much as solar and 5 times as much as wind produced in 2021. Given the increasing power demand and reliability needs, hydropower, traditionally perceived as a cheap, reliable, and carbon-neutral option, has attracted the interest of governments and investors. However, given the rapid decline in costs of other renewable power sources and the effects of climate change on water availability, many proposed hydropower projects have seen their economic viability reduced, especially in a decade as previously reported by a study in Science.


However, the previous study evaluated hydropower projects against other renewable power sources based on purely techno-economic considerations. While some hydropower projects can improve the power outlook of a region, these can also substantially alter the ecosystem they contribute to. Furthermore, whenever new reservoirs are built, the biomass available in inundated land and brought to the reservoir can be digested to produce greenhouse gas emissions, especially methane. As previous research showed, the relevance of these emissions for global climate will increase as we decarbonize the energy sector.

Given these interconnections between energy for socioeconomic development, ecosystem conservation, and climate change mitigation, the problem urges a more holistic perspective. A team of scientists at Politecnico di Milano and Stanford University set out to build a computer simulation framework to explore the sensitivity of these trade-offs to support dam planning in a way that is beneficial to humans and less detrimental to nature.


“We know that between 40% and 68% of proposed hydropower capacity is economically viable in Africa. However, average river fragmentation and reservoir emissions would increase by around 50% and 30%, respectively.”, says Angelo Carlino, lead author of the study, a postdoctoral fellow at the Carnegie Institution for Science at Stanford, previously a postdoctoral researcher at Politecnico di Milano and visiting scholar at the Natural Capital Project at Stanford University. “How much of this proposed hydropower can be replaced with other power sources to reduce these impacts?“


“We examine the trade-offs between these three objectives to strike the best trade-offs and substantially reduce these impacts at low cost”, says Rafael Schmitt, co-author of the study and lead scientist at the Natural Capital Project at Stanford University. “We found that reservoir emissions and river fragmentation impacts can be reduced by at least 50% with a negligible impact on electricity prices and total costs”.


“We can simulate the energy system and the environmental and climatic impacts using computer models”, states Anna Clark, co-author of the study and research assistant at the Natural Capital Project at Stanford University. “Artificial intelligence can be used to search and find the solutions minimizing conflicts between energy, ecosystem, and climatic objectives.”

“No more than 50% of the proposed capacity should be built when integrating techno-economic, environmental, and climatic considerations”, says Andrea Castelletti, corresponding author of the study, full professor, and head of the Environmental Intelligence Lab at Politecnico di Milano. “Solutions are becoming increasingly available to reduce hydropower impacts: from multi-objective dam planning to floating solar panels atop existing reservoirs. We will now focus on the social and political dimensions of the energy transition. Our ultimate objective is to connect continental energy and climate policy to local infrastructure design and operation.”

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