IWRA Proceedings

AbstractIntroduction: GROWA, the large scale water balance model developed in Research Centre Juelich (Kunkel and Wendland, 2002) has been applied to regions ranging typically between mesoscale river basins (approx. 1000 km2) up to entire Federal States and macroscale transboundary river catchment areas of 100,000 km2 and more (Bogena et al. 2005). As input data it required spatial distributed input data sets (e.g. soil physical parameters, land cover, topography etc., climate data). In the last years GROWA has been applied to an area-covering recalculation of natural long-term groundwater availability in the Federal States of Bremen, Hamburg, North-Rhine-Westphalia and Lower-Saxony (Kunkel et al., 2006). In theEnvironemtal Agencies and Geological Surveys of these Federal States, GROWA is used for practical water resources management related issues, e.g. the grants of water withdrawal rights to public water suppliers and for the required status reviews of the groundwater bodies according to the EU Water Framework Directive. Method: We will apply the GROWA model for the entire Federal States of North Rhine - Westphalia, Lower Saxony, Hamburg and Bremen German in order to predict the impact of climate scenarios on the groundwater resources. The model will be calibrated and validated for the hydrological period 1971 – 2000, which will represent the reference status for the scenario analyses. The climate change scenarios are generated by the Atmospheric Environmental Research Division (IMK-IFU) of Research Centre Karlsruhe and will be implemented in the GROWA model. Results: The climate change scenarios will be implemented in the GROWA model in order to predict the temporal development of mean long – term total runoff, direct runoff and groundwater runoff in Germany, including regionally differentiated analyses for river basins, regions and administrative units. Conclusions: Special emphasizes will be given to the regionally differentiated prediction of the mean long- term impacts on groundwater recharge, which determines both, the river discharge and ecological status of rivers during dry periods, as well as the upper limit for the sustainable abstraction of groundwater (e.g. prognosis of groundwater hydrograph trends in regions, where water supply is fed from groundwater).