A new tool that enables the hydropower sector to report on its carbon footprint for the first time has been launched at the 2017 World Hydropower Congress in Addis Ababa.

Developed by the International Hydropower Association, in collaboration with the UNESCO Chair for Global Environmental Change, the G-res tool adopts a new modelling methodology enabling decision-makers and stakeholders to better estimate the greenhouse gas emissions associated with the introduction of a reservoir into a landscape.

G-res is a publicly available web-based tool that allows hydropower companies, investors, consultants, decision-makers and other stakeholders to more accurately report on the net impact on GHG emissions resulting from the introduction of a reservoir in a landscape, whether for an existing or planned reservoir. 

Building upon a new conceptual framework developed in cooperation with researchers from the University of Quebec at Montreal (UQÀM), the Norwegian Foundation for Scientific and Industrial Research (SINTEF) and the Natural Resources Institute of Finland (LUKE), the tool uses a new modelling methodology based on current scientific knowledge and over 500 empirical measurements from more than 200 reservoirs worldwide. Using readily available input data, the G-res tool provides a way to assess greenhouse gas (GHG) impacts without the need for large-scale field measurement campaigns and multi-year studies.

GHG emissions from natural inland waters, i.e. streams, rivers and lakes, are significant sources of atmospheric carbon. They are of a similar scale to the carbon uptake by terrestrial and ocean bodies and therefore play a significant role in the global carbon budget. 

Carbon dioxide and methane are produced from the decomposition of organic matter by bacteria in the sediments and the water column of a water body. The creation of a reservoir alters the natural flows of a water body, and adds additional organic matter due to the flooding of surrounded areas after impoundment, increasing the decomposition of organic matter. It is important not only to accurately estimate the emissions from reservoir, but also to understand the different pathways and factors controlling them.

These can have an impact on the design characteristics of new reservoirs, and can help explain the variability in reservoir GHG emissions.

The G-res tool accounts for the net change in emissions from transformations of the natural landscape that are attributable to reservoir introduction over the reservoir’s lifetime. It does this by accounting for GHG emissions before and after the reservoir was created. The tool also accounts for the natural emissions that would have occurred downstream, but now occur in the reservoir. This reflects more closely ‘what the atmosphere sees’ as a result of the land-use change.

The G-res tool also takes into account GHG emissions from the construction of the reservoir infrastructure, including a first-order estimation of emissions due to dam construction. Finally, the G-res tool allocates emissions to the various purposes of the reservoir. Many reservoirs serve multiple purposes, including water supply, irrigation, hydropower, flood control, environmental management and pollution control. By recognising the different services offered by reservoir creation, the tool allows for improved GHG accounting of the related human activities.

“The development of the G-res tool is a major milestone in the research on GHG from reservoirs,” commented Rikard Liden, senior hydropower specialist at the World Bank. “This is the first scientifically based tool available for planners and designers to quantify reservoir emissions, which is possible to use with the limited data available in the preparation stages of a new dam. It will be a great help for the World Bank as it will enable us to estimate the carbon footprints of reservoirs at an early stage of our engagement.”



The International Hydropower Association, in collaboration with the UNESCO Chair for Global Environmental Change, launched the G-res tool on Wednesday 10 May during a focus session at the World Hydropower Congress in Addis Ababa. Information and technical documentation about the G-res tool is available at www.hydropower.org/gres.