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Climate mitigation

The challenge

There is a clear and pressing need to eliminate uncertainty in quantifying the greenhouse gas footprint of reservoirs. 

The greenhouse gas (GHG) footprint of hydropower, in particular the emissions caused by the creation of a reservoir, has long been questioned in both scientific and policy spheres.

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Up until now, there has been no consensus on how to quantify this footprint. The biochemical processes associated with the flooding of terrestrial land are very complex, and existing measurement techniques are both cumbersome and expensive.

This uncertainty has proved a significant obstacle in financing hydropower projects. There is an increasing need for policy-makers and decision-makers to better understand the GHG emissions of reservoirs.


Our strategy and action

IHA has led the way in developing a tool for reliably estimating the carbon emissions of hydropower.

Since 2006, we have partnered with UNESCO, the World Bank and leading research institutions, along with supporting members including CTG, EDF, Hydro-Québec, Landsvirkjun, Sarawak Energy and Statkraft.

We have taken a leadership role in advancing a common understanding of how GHG emissions arise from reservoirs, working closely with leading scientists.

This led, in 2017, to the launch of the GHG Reservoir (G-res) Tool for estimating net emissions from reservoirs from both before and after development. The web-based tool is publicly available online.

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We offer assisted assessments using the G-res Tool as well as dedicated training for new users. We will continue updating and refining the tool as new empirical data and scientific insights come to light.

Our goal is for the G-res Tool to become the internationally recognised methodology to reliably estimate reservoir GHG emissions and allocate emissions to other services, including hydropower generation.


Join the network

IHA’s Climate Change Knowledge Network looks to build and share knowledge on the climate mitigation potential of hydropower reservoirs. Members can receive training, support services and assisted assessments using the G-res tool at a discounted price.

Hydropower Pro

IHA members can access the knowledge network in Hydropower Pro, our online member community.

In the online group, network members can connect with each other, exchange experiences and access essential resources, briefings and case studies.

For any questions, please contact IHA senior analyst Mathis Rogner at

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