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Reliable modelling of climate–water interactions at the river basin and regional scale requires development of advanced modelling approaches at scales relevant for assessing the potential effects of climate change on the hydrological cycle. These approaches should represent the atmospheric, surface and subsurface hydrological processes and take into account their characteristic temporal and spatial scales of occurrence. The paper presents a climate change impact assessment performed for the Elbe River basin in Germany (about 100 000 km2). The method used for the study combines: (a) a statistical downscaling method driven by GCM-predicted temperature trend for producing climate scenarios, and (b) a simulation technique based on an ecohydrological semi-distributed river basin model, which was thoroughly validated in advance. The overall result of the climate impact study for the basin is that the mean water discharge and the mean groundwater recharge in the Elbe basin will be most likely decreased under the expected climate change and diffuse source pollution will be diminished. Our study confirms that the uncertainty in hydrological and water quality responses to changing climate is generally higher than the uncertainty in climate input. The method is transferable to other basins in the temperate zone.

During the last two decades significant socio-economic and environmental changes took place in Central and Eastern Europe (CEE), including collapse of the old socio-economic systems and climate change. The main objective of the paper is to analyse changes in water resources in the region and to relate them either to ongoing climate change or to socio-economic changes in the region, where possible. Two basins located in the Eastern part of Germany and in the Western part of Poland were taken as case study areas. An attempt to compare changes of water resources triggered by socio-economic and environmental (therein climate) changes was undertaken, including quantitative assessment of relative magnitudes of impacts, where feasible. The impacts on both water quantity and water quality aspects were investigated, considering changes in river discharge, groundwater dynamics, water demand, point and non-point source pollution in both basins under study. Where necessary, the analysis of data was supported by modelling results. The analysis reported confirms that until now the changes in socio-economic systems have impacted regional water resources in a more significant way than the climate change. However, the impacts of climate change on water resources in the study regions are likely to increase in the future, warmer climate, as projected by the existing scenarios.

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Abstract. This article describes a modelling study on nitrogen transport from diffuse sources in the Nuthe catchment, representing a typical lowland region in the north-eastern Germany. Building on a hydrological validation performed in advance using the ecohydrological model SWIM, the nitrogen flows were simulated over a 20-year period (1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000). The relatively good quality of the input data, particularly for the years from 1993 to 2000, enabled the nitrogen flows to be reproduced sufficiently well, although modelling nutrient flows is always associated with a great deal of uncertainty. Subsequently, scenario calculations were carried out in order to investigate how nitrogen transport from the catchment could be further reduced. The selected scenario results with the greatest reduction of nitrogen washoff will briefly be presented in the paper.