the impact of reservoirs on natural greenhouse gas (GHG) emissions in a river basin. To date, the Project has involved some 160 researchers, scientists and professionals, from more than 100 institutions. The overall objective of the project is the evaluation of changes in GHG emissions due to the impoundment of freshwater reservoirs. The project deliverables include: Development of measurement guidance for the evaluation of any change in the pre-existing greenhouse gas emissions Promotion of scientifically rigorous measurements on a representative set of reservoirs (in accordance with the above guidance) and recording of the results in a common database Development of predictive modelling tools to assess the GHG status of unmonitored reservoirs and potential new reservoir sites Development of mitigation guidance for vulnerable sites. A key milestone in the project was the publication, in 2010, of the GHG Measurement Guidelines for Freshwater Reservoirs, a comprehensive tool to assess the GHG status of freshwater reservoirs, describing standardised procedures for field measurements and calculation methods to estimate the impact of the creation of a reservoir on a river basin's overall GHG emissions. The application of these Guidelines to a set of representative reservoirs worldwide allows the building of a reliable, standardised results database, in order to develop the basis for predictive modelling capability. Since then, IHA has been involved through this project in the development of a risk screening tool, the GHG Reservoir Screening Tool, that will allow for rapid and low-cost assessment of likely GHG emissions from reservoirs. This will allow developers and operators to assess whether a reservoir is likely to generate emissions, and therefore require further and more detailed examination and modelling. A revised version of the tool, G-Res, will allocate emissions to the particular services provided by the reservoir. A prototype of the revised tool was launched at the World Hydropower Congress in Beijing, in May 2015. The tool is intended to inform decision makers if there is likely to be any significant GHG footprint associated with the purposes for which the reservoir is being developed. The tool will be applicable for both existing and planned reservoirs. If the tool identifies a reservoir that is likely to cause a significant impact, the recommended action will include the possibility of detailed modelling. The GHG Screening Tool provides an estimate of the likely level of total (gross) GHG emissions from a freshwater reservoir. It has been developed as an empirical model,