Greenhouse gas emissions from lakes and reservoirs have been studied intensively in recent years. A particular focus has been on methane because methane emissions from lakes are a large source in the global methane budget. The main pathways of the methane emitted from lakes are diffusive transport across the water surface and ebullition. I will present investigations of methane distributions in lakes and reservoirs and discuss emissions via the different pathways.
An emphasis will be on the question about the origin of the methane emitted by diffusion from the open water of lakes, which is still discussed controversially. I will provide arguments supporting that transport from the littoral zone of lakes and not production in the open surface water is the source of surface water methane during the stratified season. I will additionally show examples on ebullition fluxes and, depending on time, will discuss greenhouse gas emissions from a hydropower reservoir.