Development of an operational drought forecasting system using couples models for groundwater, surface water and unsaturated zone

During periods of drought the National Coordinating Committee for Water Distribution of the Netherlands has to decide how the available surface water is used and allocated between different functions. To support decision making, real-time information is needed about the availability of surface water, groundwater levels, saturation of the root zone, etc. This real-time information must give insight into the current state of the system as well as into its state in the near future. For this purpose an operational drought forecasting system has been implemented. This system runs on a daily basis and provides distributed model estimates and forecasts of hydrological variables for the whole of the Netherlands. The model consists of a nationwide distribution model and surface water model coupled with a MODFLOW-MetaSWAP model of the saturated-unsaturated zone (250x250 m2). Model forcing includes radar data of actual precipitation and point measurements of actual evaporation. Model forecasts are driven by precipitation and evaporation from the Ensemble Prediction System. Each day 50 model runs are performed in parallel to calculate 10-day forecasts based on the ensemble members of the EPS. The system is operationalized within Delft-FEWS, which is an operational forecasting system to manage data and models in a real-time environment.