peer reviewed ; The management of urban rivers which drain contaminated groundwater is suffering from high uncertainties regarding reliable quantification of groundwater fluxes. Independent techniques are combined for estimating these fluxes towards the Zenne River, Belgium. Measured hydraulic gradients, temperature gradients in conjunction with a 1D-heat and fluid transport model, direct flux measurement with the finite volume point dilution method (FVPDM), and a numerical groundwater flow model are applied, to estimate vertical and horizontal groundwaterfluxes and groundwater–surface-water interaction. Hydraulic gradient analysis, the temperature-based method, and the groundwaterflow model yielded average verticalfluxes of–61,–45 and–40 mm/d, respectively. The negative sign indicates upwardflow to the river. Changes in exchangefluxes are sensitive to precipitation but the river remained gaining during the examined period. The FVPDM, compared to the groundwaterflow model, results in two very high estimates of the horizontal Darcyfluxes (2,600 and 500 mm/d), depending on the depth of application. The obtained results allow an evaluation of the temporal and spatial variability of estimated fluxes, thereby helping to curtail possible consequences of pollution of the Zenne River as final receptor, and contribute to the setup of a suitable remediation plan for the contaminated study site. ; Flux-based Risk Assessment of Contaminant on Water resources and ECOsystems FRAC-WECO SD/TE/02