This chapter discusses a multi-model ensemble simulation is generated by using the multiple data sources for land use and soil type and for rainfall and evapotranspiration. It shows that the multi-model ensemble generated from multiple data sources for catchment characteristics and hydrometeorological input, improved the simulation of discharge from the Rijnland water system. The method was applied with the physically-based spatially distributed SIMGRO model of Rijnland, which was parameterised based on expert judgement, with limited calibration. The SIMGRO base model, with the Thiessen polygon rainfall, European database soil map and Landelijk Grondgebruik Nederland land-use map is the member of the ensemble. The soil maps have a higher influence in summer, with the models with Dutch database data showing better performance than the models with European database.