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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 reservoirs, has long been questioned in both scientific and policy spheres.

Up until now, there has been no consensus on how to quantify this footprint.

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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 and decision makers to better understand the GHG emissions of reservoirs.


Our strategy and action

IHA has led the way in developing a tool to reliably estimate 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 Quebec, 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 G-res tool for estimating net emissions from reservoirs from both before and after development. 

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Throughout 2018, we will continue to offer assisted assessments using the G-res tool and dedicated training for users. We will also be updating and refining the tool as new empirical data and scientific insights come to light.

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


Recent activities

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In May, the G-res tool was officially launched during the 2017 World Hydropower Congress in Addis Ababa. During the launch, preliminary G-res tool results for nearly 500 hydropower reservoirs were presented, emphasising the importance of multi-purpose reservoirs for development.

In November, the conceptual framework underlying the G-res tool methodology was published in the peer-reviewed journal Ecosystems.

In November, the G-res tool was presented at the Canadian Hydropower Forum in Canada.

In November, the G-res tool hydropower results were presented at the Enhancing Sustainability in Hydropower Development conference in Colombia.


Join the network

IHA’s Climate Mitigation 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.

If you are an IHA member, you can join the Climate Mitigation Knowledge Network

Contact us

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

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