Climate impact of tropical hydropower: a perspective on G-res model calculations

Abstract

Despite environmental and social issues, hydropower has been promoted as a climate-friendly form of electricity generation. This perspectives paper shows that such a claim needs to be considered with great care, especially in tropical, low-latitude areas. First, because complete climate impacts are rarely considered. For instance, the frequently cited IPCC (2014) emission intensities omit biogenic CO₂ emissions from reservoirs. The openly available G-res tool provides an opportunity to partly fill this gap. Second, individual cases show huge variability in climate impacts. In this paper, we discuss the results of G-res calculations for three projects in Myanmar, which confirm this large variability. Several international guidelines suggest to use G-res to estimate a hydropower project's climate impact. However, an analysis of the methodology shows that the G-res calculations can substantially underestimate the GHG emissions of hydropower projects due to its limitations and assumptions. Furthermore, the Earth's albedo change by the reservoirs needs to be considered. We show that the impact thereof is of comparable magnitude and variability. As a result, in many cases in the tropics hydropower will have considerably larger climate impacts than solar and wind and can even exceed those of fossil fuel installations.