Report of Research Training Group (GRK 2032) Urban Water Interfaces (UWI)

Water quality and quantity in urban areas face multiple threats such as climate change, ongoing urbanisation and diverse contaminations. Berlin has served as an ideal ‘natural laboratory’ for our water research, as its water system is highly stressed, for example, by small river discharges, a high use of bank filtration, partially closed water cycles as well as strong interactions of compartments, natural and technical systems. Urban water interfaces (UWI) play a key role in the urban water cycle linking these compartments and systems and thus markedly affect the overall system behaviour. As there were considerable gaps in related research and qualification, the Research Training Group UWI set up a unique close collaboration of principal investigators (PI) affiliated with the Technische Universität Berlin and the Leibniz Institute of Freshwater Ecology and Inland Fisheries, together with strong partners such as the Berliner Wasserbetriebe (BWB). The educational goal for the doctoral researchers from engineering and natural sciences was a new quality of interdisciplinary knowledge with a strong international orientation within a structured framework. We have established four Common Topics to enhance the collaboration among doctoral researchers and PIs: Interfaces in Urban Watersheds, in Urban Freshwater Ecosystems, in Urban Hyporheic Zones and in Sewer Systems. From the qualification programme, we would like to highlight: three newly developed Core Courses which ensured that all doctoral researchers received a common educational foundation across the different disciplines, the Common Topics mentioned above, and the Student Research Council established by the doctoral researchers to foster collaboration within their group by various self-organised activities. Scientific progress was based on: (i) advancing our understanding of interfacial processes and their quantitative impact on the urban water cycle, (ii) predicting impacts of future changes and (iii) detecting vulnerable conditions for adaptation, resilience and improved management. We established innovative links between empirical methods, experiments (lab, field) and modelling (conceptual, numerical, machine learning) to describe the relevant processes on different scales in space and time and across scales. Many of the results could only be achieved through the close collaboration between engineers and natural scientists resulting in a ‘new normal’ in interdisciplinary thinking. UWI became a nucleus to which other projects connected. Overall, 19 doctoral researchers (funded by UWI) and 8 kollegiates (funded by other sources) completed their doctoral theses; we expect another 11 and 2 to finish in the future; 137 peer-reviewed papers and 266 other publications have been published. All of the UWI graduates have secured challenging positions in academia, water engineering practice or administration. It is particularly remarkable that five UWI graduates have already obtained professorships.