Interaction processes between surface water (SAW) and groundwater (GW) represent an essential component in the overall water balance and thus also in the material balance in the Havel region. During the infiltration of river water into the aquifer a multitude of physical, chemical and biological processes take place. The infiltration of SAW into the GW depends on the hydraulic conditions, the hydrogeological aquifer properties and the structural structure and degree of colmatisation of the river beds. Hydraulic engineering interventions that influence the composition of the river bed can significantly change the interaction between SAW and GW as well as the associated water and material flows. At the research site Brandenburg, large-scale tracer experiments in combination with numerical modeling will be used to identify and quantify hydraulic engineering interventions with regard to the expected effects on water and material flows between SAW and GW.