Catchment model regionalization approach based on spatial proximity: Does a neighbor catchment-based rainfall input strengthen the method?

Study region: The Upper Rhine-Meuse catchment (French part). Study focus: A rainfall input-related sensitivity analysis was conducted to assess if, with a neighbor catchment-based knowledge of optimal rainfall input, rainfall-runoff modeling becomes more competitive for estimating streamflow at ungauged catchments. New hydrological insights for the region: Results show that when streamflow is known at the outlet of a catchment, optimal rainfall input for a lumped catchment model is mostly computed with a subset of raingages. When streamflow is unkown at the outlet of a catchment, a regionalisation approach of model parameter values based on spatial proximity is not able to take advantage of a neighbor-catchment based knowledge of optimal rainfall input. This report encourages to search for a catchment model regionalization approach based on spatial proximity which makes no explicit use of measured rainfall to estimate streamflow at an ungauged location.