EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The albedo-climate penalty of hydropower

Albin Hammerle1, Enrico Tomelleri2, and Georg Wohlfahrt1
Albin Hammerle et al.
  • 1University of Innsbruck, Ecology, Innsbruck, Austria (
  • 2Faculty of Science and Technology, Free University of Bolzano, Bolzano, Italy.

Limiting global warming to less than 2°C relative to preindustrial times by the end of this century requires a rapid and long-lasting decarbonization. In contrast to the other major renewable energy sources, solar and wind, hydropower reservoirs allow storing energy and releasing it when required, a significant advantage for stabilizing electrical grids. The establishment of hydropower reservoirs typically involves a land-use change when formerly terrestrial ecosystems are inundated. One, hitherto overlooked, consequence of this land-use change is a decrease in surface albedo, as waterbodies are characterized by a lower albedo compared to most terrestrial ecosystems. The main objective of this study is to quantify the positive radiative forcing resulting from this albedo change and to oppose it with the negative radiative forcing resulting from the fossil fuel displacement by the hydropower electricity generation. To that end, we compiled, on the basis of publicly available datasets, a global database of hydropower reservoirs. The hypothetical change in albedo associated with their construction was assessed on the basis of the difference in remotely sensed albedo (MODIS MCD43A1) between the hydropower reservoir and the surrounding landscape. We then calculated the break-even point, that is the time required for the time-integrated negative radiative resulting from the fossil fuel displacement to offset the positive radiative forcing from the albedo difference. The major result from this study is that break-even times range from less than a year up to several years and even a few decades. The key metric governing these differences is the annual electricity generation to reservoir surface area ratio, low ratios resulting in unfavorably long break-even times. Additional influence factors having a modulating influence are latitude, governing the incident solar radiation, and the magnitude of the albedo difference. We conclude that the displacement of fossil fuels by hydropower wins over the albedo penalty in the long-term. In the short-term, and thus for contributing towards the goal of a rapid decarbonization, the albedo penalty may be dominating and needs to be considered in the design of hydropower plants.

How to cite: Hammerle, A., Tomelleri, E., and Wohlfahrt, G.: The albedo-climate penalty of hydropower, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19483,, 2020

Display materials

Display file

Comments on the display material

AC: Author Comment | CC: Community Comment | Report abuse

Display material version 2 – uploaded on 05 May 2020
corrected for typos
  • CC1: Comment on EGU2020-19483, Jonathan D. Muller, 07 May 2020

    The replacement of fossil fuels by hydropower could be considered "equivalent" to carbon removal. Wouldn't that be an important factor in the calculation?

    • AC1: Reply to CC1, Georg Wohlfahrt, 07 May 2020

      Hi Jonathan,

      exactly, the generation of hydroelectricity is a kind of carbon removal, because fossil fuels are replaced. What we did is to oppose the negative radiative forcing from the fossil fuel displacement with the positive radiative forcing from the albedo change. 


Display material version 1 – uploaded on 05 May 2020, no comments