Water flow and heat transport modelling at the interface between river and aquifer The functioning of the surface water groundwater interface as buffer filter and reactive zone is important for water quality ecological health and resilience of streams and riparian ecosystems. Solute and heat exchange across this interface is driven by the advection of water. Characterizing the flow conditions in the streambed is challenging as flow patterns are often complex and multidimensional driven by surface hydraulic gradients and groundwater discharge. This thesis presents the results of an integrated approach of studies ranging from the acquisition of field data the development of analytical and numerical approaches to analyse vertical temperature profiles to the detailed fully integrated 3D numerical modelling of water and heat flux at the reach scale. All techniques were applied in order to characterize exchange flux between stream and groundwater hyporheic flow paths and temperature patterns. The study was conducted at a reach scale section of the lowland Selke River characterized by distinctive pool riffle…