Lay summary
This Ph.D. project addresses two main questions:1.What are the main biogeochemical and physical factors driving high rates of methane ebullition from reservoir sediments?2.How can the ebullition pathways be effectively quantified?The study will provide a strong methodological basis and yield insights into the processes governing methane fluxes in two contrasting hydropower reservoirs on the Aare and the Zambezi Rivers.During the last part of this ongoing PhD project we will take advantage of two opportunities: 1) We are collaborating with specialists for atmospheric flux measurements in order to cross-validate our methods for short time scales at our Swiss field site on Wohlensee. 2) An ongoing interdisciplinary project on hydropower reservoirs on the Zambezi Basin offers the opportunity to contrast our detailed process study in Switzerland with an analysis of Lake Kariba in the Zambezi basin. This subtropical reservoir is characterized by a completely different climatic and hydrological setting and shows clear hot spots of methane emissions.