Hydropower Reservoir Greenhouse Gas Emissions: State of the Science and Roadmap for Further Research to Improve Emission Accounting and Mitigation

Rapidly decarbonizing the electricity grid is crucial for achieving net-zero greenhouse gas (GHG) emissions by mid-century and mitigating climate change impacts. Hydropower facilities can directly support grid decarbonization; however, like all energy systems, they emit GHGs throughout their lifecycle, with reservoirs being an important source. Further research is urgently needed to improve the accounting and mitigation of hydropower reservoir GHG emissions to ensure that this technology is accurately considered in decarbonization policies and to allow project owners and energy buyers to make credible emission claims regarding this energy source. To this end, this paper reviews over seven dozen studies and emerging research to synthesize the current state of the science on reservoir GHG emission pathways as well as advancements in emission measurement tools to identify areas where further research is needed. This paper presents a research roadmap for government agencies, research institutions, and funding organizations covering four action areas: understanding and reducing uncertainties in reservoir GHG estimation and associated publicly accessible estimation tools; reducing the technical and economic barriers for reservoir managers to use GHG estimation tools; setting common standards to enable consistent monitoring, allocation, and reporting of reservoir GHG emissions; and supporting work on reservoir GHG emission mitigation strategies, including watershed-scale strategies. Progress in these areas will enable robust accounting of hydropower reservoir GHG emissions and targeted mitigation efforts to advance grid decarbonization.