Hillslope-scale exploration of the relative contribution of base flow, seepage flow and overland flow to streamflow dynamics

Surface and subsurface flows interact at different spatial temporal scales through the development of saturated areas occurring when aquifer reaches surface. While this interaction exerts a strong control in partitioning water between base flow, seepage flow overland its quantification remains challenge. Here, we propose novel modeling approach based on two equivalent hillslopes to capture variabilities main processes. We calibrate their hydraulic properties dynamics stream discharge. The model is tested pilot catchments located Brittany (France). For both catchments, successfully calibrated 40 years discharge data. results demonstrate that contrasted are required, with: (1) relatively low conductive hillslope (conductivities 3x10–8 m/s 2x10–6 m/s) enhancing during recharge periods while also sustaining late recession period slow discharge, (2) highly diffusive (diffusivity 5x10–3 m2/s 3x10–1 m2/s) dominantly shaping event- seasonal-scale streamflow behavior. contrast reveals fundamental role heterogeneity controlling groundwater storage-discharge functions, ruling out any homogeneous catchment scale. Low appear be non-obvious combination contributions hillslopes, less catching up more one by end period. Catchment-scale responses integrate complex interactions recharge, volume storage extent area.