Seasonal discharge forecasting for the Upper Danube

Study Region: The authors contributed with a seasonal forecast system for discharge in the case study area of the Upper Danube basin upstream of Vienna. The basin, with a drainage area of approx. 100.000 km2, is characterized by complex topography dominated by the Alps. Study Focus: New advances in the mean term (seasonal) climate forecasting increase the potential of seasonal hydrological forecasting. In the frame of an European project (Clim2Power, 2020) a climate service for the assessment of seasonal energy production of renewable resources was developed. Seasonal discharge forecasts are generated using a dynamical approach running the hydrological model COSERO with forecasted climate inputs provided by Germany’s National Meteorological Service (Deutscher Wetterdienst – DWD). The seasonal climate forecasts are based on a large ensemble of daily predictions available up to 6 months in the future. These forecasts are downscaled to a spatial resolution of 6 km. The following analysis is based on aggregation of these daily values to monthly and seasonal values. New Hydrological Insights for the Region: Downscaled historical forecasts (hindcasts) and historical discharge observations over the last 15 years are used to assess the skill of the seasonal forecast in several Alpine basins. In general, the results show a limited skill. Therefore, the seasonal discharge forecasting system in this region is still not sufficient to incorporate the results into water resources decision support systems