Methane emissions from freshwater reservoirs represent a globally relevant greenhouse gas source and represent approximately 6% of total human-caused methane emissions. In addition, this contribution will grow in the coming decades with over 3,700 future hydropower dams either planned or under construction as well as climate induced feedbacks likely to increase emission rates. However, there is high uncertainty in estimating reservoirs emissions from the local through to global scales. This is due to a combination of data paucity in key regions, particularly in the Southern Hemisphere, as well as the challenge of monitoring emission pathways. There are two major emission pathways, ebullition and diffusive fluxes, but ebullition rates are 2 to 5 orders of magnitude higher than diffusive fluxes and occur sporadically over small zones within reservoirs. Spatial weighting of these fluxes is critical to confidently estimating total reservoir emission rates. The key to improved spatial weighting of rates is to better understand the primary drivers of different emission pathways and, in particular, the ebullition pathway. We will provide an overview of a 15‑year research program examining methane emissions and key drivers from 16 freshwater reservoirs located in the Southern Hemisphere sub-tropical (South East Queensland) and temperate (Tasmania) regions. We show the contribution of ebullition to be highly variable, ranging from 10% to over 90% of total reservoir emissions, as well as being the dominant pathway in the majority of reservoirs (12) studied. In addition, we identify reservoir drawdown, air pressure changes and catchment organic loading as key drivers of ebullition. Finally, we detail a scalable approach to undertake regional and global empirical studies and greatly reduce the uncertainty associated with methane emissions from freshwater reservoirs. These findings will be of broad relevance to corporate and government entities navigating the complexities in estimating annual greenhouse gas emissions from reservoirs.