Urban Rivers, Hidden Signals: Feeling the Pulse of Contaminants in Bank-Filtrated Water

Bank filtration has been applied worldwide to extract raw river water after a passage through subsurface sediments. Commonly, this water is used as drinking water after proper treatment. However, river water, especially if urban structures are part of their catchment, is prone to anthropogenic impacts possibly leading to unwanted chemical substances and compounds in water. A wide range of impacting boundary conditions, e.g., high or extreme low river water levels affect the spatio-temporal evolution of the resulting concentrations in groundwater. In order to improve the understanding in the key impacts influencing the concentration behavior in the extracted water at bank filtration sites, the following steps are applied in this study using a highly urbanized site at Düsseldorf, North-Rhine Westphalia, Germany: Firstly, conceptual models are set-up based on delineation of widely known principles at comparable sites. On the basis of these conceptual models, in a second step hypotheses are made for the spatio-temporal behavior of hydraulic and hydrochemical parameters in the groundwater for a set of scenarios often occurring in river catchments. The resulting assumptions and signals expected from the conceptual models under certain conditions were compared to field data from the water supply company Stadtwerke Düsseldorf and City of Düsseldorf and later-on analyzed using a 2D-vertical numerical model. Finally, improvements in the understanding of the processes can be achieved. Besides this, understanding will help to improve observation information quality by reducing efforts in the same time.