This project aims at developing a new transient model for Lake Kivu that considers the dynamic properties of the lake. The model will be used to
- derive a range of possible scenarios for the history of the lake in the last 1000 years that has led to the present conditions
- estimate the most probable development of the lake in the future for selected CH4 extraction scenarios under a range of different climatic conditions
- assess the contributions of the CH4 extraction, the hydrological processes and climatic conditions on the uncertainty of these projections.
The development of the new model relies on novel measurement and modelling techniques that have emerged in the last decade and will be further advanced during this project, as well as on the availability of observational data from preceding research projects on Lake Kivu. For the purpose of quantifying the transport and mixing processes in the lake based on geochemical data, we will couple our successful 1-dimensional physical lake model Simstrat via the Framework for Aquatic Biogeochemical Models (FABM) to the Aquatic EcoDynamics Modelling Library AED, of the University of Western Australia.
The already available data from our previous projects will be complemented with vertical profiles of the concentrations of dissolved gases (noble gases, CH4, carbon dioxide) in the lake. For this purpose, we will adapt the portable field mass-spectrometer which was recently developed by the Environmental Isotopes research group at Eawag for vertical profiling in deep lakes. The newly acquired gas measurements will enable us to better constrain the vertical transport processes between the deep water and the near-surface water and to quantitatively assess the influence of the subaquatic groundwater discharge on the lake-internal processes.