An important shortcoming of modelling tools that are used for managing hydro(geo)logical problems is that the tools are focusing on one specific compartment of the terrestrial system such as the groundwater, the soil water, or the surface water. However, the management of complex water related problems requires a holistic approach that considers the interactions between the different compartments at local and regional scales. For instance, the soil water status at a farmer’s field is influenced by the groundwater level whereas groundwater levels depend on the interaction with the surface water and on groundwater recharge and water infiltration and percolation through the soil in a larger area. Local measures that influence the water infiltration and surface water levels have an impact on the local soil water balance and groundwater recharge and influence groundwater levels and storage at a larger scale. These interactions between different compartments and acting at different spatial and temporal scales can be represented in fully coupled hydrological models of the terrestrial system that consider groundwater, soil, vegetation, and atmosphere. Using physics-based models, that solve mass and energy balance equations based on gradient-based estimates of fluxes, the different compartments can be coupled straightforwardly and consistently and information about the geology, soil types, vegetation, and topography of the region can be included in the model, in principle without calibration. One of the big advantages of physics-based models is that local changes can be related directly to parameter changes of the model so that their impact on the terrestrial water balance can be evaluated directly without requiring data about the reaction of the system to such changes that are needed to re-parameterize the model.
A coupled model integrating groundwater, surface water (ParFlow), and landsurface-atmosphere interactions (CLM) has been setup for central Europe including Germany, the Benelux (covering the entire Scheldt and Meuse catchments), Switzerland, Austria, and the Czech Republic. The model is parameterized using harmonized geological (International Hydrogeological Map of Europe) and soil data (SoilGrids texture), using generic land use classes, and topography at a spatial resolution of 611 by 611 m. This model is implemented on the GPU booster of the Jülich Supercomputer Centre and driven by atmospheric forecasts obtained from the ECMWF. It provides 10-day forecasts of the hydrological status of the terrestrial system (wassermonitor) and a time series of 10 years providing a climatology of hydrological variables such as water storage and groundwater level.
We give a short demonstration of the model and present simulated timeseries of groundwater levels and subsurface water storage for a set of sites in Flanders and Germany.