Challenges and solutions for assessing the impact of freshwater reservoirs on natural GHG emissions

Results from twenty years of studies of greenhouse gas (GHG) emissions from reservoirs show the importance of GHG emissions from reservoirs at a global scale, as well as the difficulties in properly estimating their effects. Despite strong efforts to build consensus in assessing the GHG status of reservoirs, many uncertainties still remain due mainly to the lack of standard measurement techniques and standard tools for assessing net GHG exchanges from reservoirs, and limited reliable information from a sufficient variety of sources. International collaborative initiatives, such as the UNESCO/IHA GHG Research Project (GHG Status of Freshwater Reservoirs) and the IEA Hydro Annex XII Task 1 (Managing the Carbon Balance in Freshwater Reservoirs), came as responses to these challenges by aiming to improve understanding of the impact of reservoirs on natural GHG emissions through the proposal and use of standardised techniques for measuring emissions in the field and for assessing the global changes of GHG emissions resulting from the creation of reservoirs.