G-res: new tool for measuring carbon footprint of reservoirs

10 May 2017 - The G-res tool was launched today at the 2017 World Hydropower Congress in Addis Ababa. G-res enables decision-makers and stakeholders to better estimate the greenhouse gas emissions associated with the introduction of a reservoir into a landscape.

Yves Prairie

Launched by IHA in collaboration with the UNESCO Chair for Global Environmental Change, this publicly-available, web-based tool can be used to measure net greenhouse gas (GHG) emissions on existing or planned reservoirs.

GHG emissions from natural inland waters, such as streams, rivers and lakes, are significant sources of atmospheric carbon. The creation of a reservoir alters the natural flows of a water body, adding additional organic matter due to the flooding of surrounding areas, which generates carbon dioxide and methane during decomposition. Current research indicates that on average, 75 per cent of CO2 emissions observed on reservoir surfaces can be considered natural, meaning they would have occurred even if the reservoir had not been created. Methane emissions, meanwhile, present a much more significant environmental challenge.

Accurate estimation of the emissions from reservoirs and understanding the factors that contribute to these are essential for determining the design characteristics of new reservoirs, and for explaining variability in emissions between reservoirs. The G-res tool can be used to calculate the net change in emissions that can be attributed to the creation of a reservoir. It therefore offers a reliable picture of the real environmental impact of the creation of a reservoir.

G-res also takes into account emissions generated by reservoir construction, and by recognising the different services offered by reservoir creation, the tool allows for improved GHG accounting of associated human activities. Many reservoirs serve multiple purposes, including water supply, irrigation, hydropower, flood control, environmental management and pollution control.

The tool builds on a conceptual framework developed by researchers from the University of Québec at Montreal (UQÀM), the Norwegian Foundation for Scientific and Industrial Research (SINTEF) and the Natural Resources Institute of Finland (LUKE). It utilises a new modelling methodology based on current scientific knowledge and over 500 empirical measurements from over 200 reservoirs worldwide.

Find out more about the G-res tool at

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