FOR 5288:  Fast and invisible: Conquering Subsurface Stormflow through an Interdisciplinary Multi-Site Approach

• Subject Area: Geosciences
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 453746323

Where does water go when it rains? Where are floods generated and how? What controls stream water quality during events? These questions are important to many fields from engineering and flood protection to water and ecosystem management and prediction of impacts of global change. The most elusive processes in the process-ensemble underlying these questions is subsurface stormflow (SSF), the fast event response triggered by lateral subsurface flow. SSF is prevalent and a more important process than generally accounted for because a basic understanding based on systematic studies across scales and sites is still lacking. However, only with systematic studies will it be possible to really advance our understanding by discovering general principles of SSF functioning and to provide protocols and best practices for its assessment, both experimentally and with respect to modelling. In Phase I of the Research Unit, we have started a systematic study of SSF by creating a unique monitoring infrastructure which includes 12 trenches of 15 m length and 3 m depth and hundreds of observation wells and stream gauges. This replicated design across different landscapes and land uses now allows a systematic study of SSF in different environments and across scales. The monitoring setup was and will be complemented by extensive sampling, a large number of experiments and the development of novel methods, from tracers to monitoring systems. This will be followed by a thorough evaluation of methods and possible proxies as well as model intercomparison, evaluation and improvement. Where standard single research projects investigate part of this puzzle at a specific location, this Research Unit provides the unique opportunity of fitting a large number of puzzle pieces together. The Research Unit will continue to have a strong emphasis on collaborative and interdisciplinary experimental work in four different test catchments that then directly feeds into a collaborative modeling effort using different modeling approaches, which in turn influences experimental design in an iterative process. Phase II will now include stepping up in scale to assess impacts beyond the headwaters, assessing the anthropogenic impacts on this process, but also comparison with other catchments worldwide. In Phase II we will strongly profit from the unique infrastructure created in Phase I to continue our work on the four challenges: 1) Development of novel experimental methods,2) Spatial patterns of SSF, 3) Thresholds and cascading effects of SSF, 4) Impacts of SSF.

• DFG Programme: Research Units
• International Connection: Austria, Canada, Italy, Switzerland, United Kingdom, USA

Projects

• Coordination Funds (Applicant Chifflard, Peter )
• Project E CONNECT - Longitudinal Patterns of SSF-Stream Connections (Applicants Blume, Theresa ;  Weiler, Markus )
• SSF FORCING - Temporal dynamics and land use effects of SSF - Irrigation experiments combined with ERT measurements (Applicant Weiler, Markus )
• SSF Model Benchmarking: Towards a robust parameterization of subsurface stormflow in hydrological models at the catchment scale (Applicants Hartmann, Andreas ;  Reinhardt-Imjela, Christian )
• SSF Novel Tracers - Biogeochemical tracers (environmental DNA, dissolved organic matter) and their transport and transformation across the hillslope–riparian–stream continuum (Applicants Chifflard, Peter ;  Schadewell, Yvonne )
• SSF Patterns and Proxies - Combining static landscape patterns, dynamic proxies and an uncalibrated process-based modeling framework to identify SSF response units (Applicants Blume, Theresa ;  Weiler, Markus )
• SSF SUBSURFACE CONTROLS: Imaging subsurface flow path dynamics in high resolution (Applicant Klotzsche, Anja )
• SSF Transform - Understanding the transformation of subsurface stormflow from hillslopes through the riparian zone (Applicants Blume, Theresa ;  Hopp, Luisa )

• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Spokesperson: Professor Dr. Peter Chifflard