Carbon-Efficient River Restoration: Clogging and Microbial Pathways

• Applicants: Professorin Sara Kleindienst, Ph.D.; Dr. Sebastian Schwindt
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Geotechnics, Hydraulic Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 562997827

In view of the climate crisis, this research project investigates greenhouse gas emissions from anthropogenically modified, clogged rivers with regard to physico-chemical and microbiological causes for the implementation of carbon-efficient river restoration. Current hydraulic engineering practices typically view microbial activities in river ecosystems as input-output systems, overlooking critical biodynamic processes that influence carbon cycling and emissions in river ecosystems. The aim of this project is to investigate microbial mechanisms in heavily degraded, clogged river ecosystems, to not only quantify carbon emissions, but also to understand their causes in order to manage them effectively. To this end, the project will combine hydraulic engineering and microbiological expertise to analyse clogged river ecosystems through field surveys, numerical simulations and laboratory experiments. Riverbed clogging refers to the filling of pore spaces in naturally coarse-grained sediment matrices by fine sediments, which disrupts vertical hydrological exchange in ecologically sensitive alpine and midland rivers. Clogging results from increased inputs of fine sediment, exacerbated by human activities such as the retention of coarse sediment behind dams or increased production of fine sediment due to erosive land use practices. This disruption of vertical exchange processes affects oxygen levels in the riverbed, which in turn alters the composition and activity of microbial communities. Oxygen is critical for microbial processes that contribute to the reduction of greenhouse gases, particularly for methane-reducing microbial communities whose activity is inhibited by restricted oxygen supply caused by clogging. The project will investigate the effectiveness of hydraulic engineering restoration measures to alleviate riverbed clogging, especially with regard to the establishment of niches for methane-reducing microorganisms. The interdisciplinary field surveys, numerical simulations and laboratory experiments will systematically analyse and unravel complex interactions between declogging restoration measures and microbial processes. New ground-breaking findings are expected on the effectiveness of restoration measures, which are important not only from a fish-ecological point of view, but also with respect to the climate.

• DFG Programme: Research Grants