Eco-hydrological water quality modeling for integrated water resources management of river basins should include all necessary landscape and in-stream nutrient processes as well as possible changes in boundary conditions and driving forces for nutrient behavior in watersheds. The study aims to assess possible impacts of the changing climate (ENSEMBLES climate scenarios) and/or land use conditions on resulting river water quantity and quality in the large-scale Elbe river basin by applying a semi-distributed watershed model of intermediate complexity (SWIM) with implemented in-stream nutrient (N+P) turnover and algal growth processes. The calibration and validation results revealed the ability of SWIM to satisfactorily simulate nutrient behavior at the watershed scale. Analysis of 19 climate scenarios for the whole Elbe river basin showed a projected increase in temperature (+3 °C) and precipitation (+57 mm) on average until the end of the century, causing diverse changes in river discharge (+20%), nutrient loads (NO₃-N: −5%; NH₄-N: −24%; PO₄-P: +5%), phytoplankton biomass (−4%) and dissolved oxygen concentration (−5%) in the watershed. In addition, some changes in land use and nutrient management were tested in order to reduce nutrient emissions to the river network.

Coastal areas will be exposed to increasing risks over coming decades due to climate change and sea-level rise. Our study focuses on the Vistula Lagoon located in the south Baltic, whose water regime and ecological status are highly dependent on the river inflow coming from its catchment. Changes in climate may cause variations in water quantity and quality in the rivers and affect the ecological and socio-economic potential of the lagoon. The climate impact study in this catchment containing more than 20 rivers is challenging as only a few of them are gauged. The impacts were modelled, using the ecohydrological model SWIM, and applying a set of 15 climate scenarios from the ENSEMBLES project. Scenario analysis revealed a projected overall increase in precipitation, as well as in temperature, for the Vistula Lagoon catchment, which cause diverse changes in discharge, water temperature, dissolved nutrient concentrations and loads coming from the rivers.

Climate projections agree on a dryer and warmer future for the Mediterranean. Consequently, the region is likely to face serious problems regarding water availability and quality in the future. We investigated potential climate change impacts, alone (for three scenario periods) and in combination with four socio-economic scenarios (for the near future) on water resources in a Mediterranean catchment, whose economy relies on irrigated agriculture and tourism. For that, the Soil and Water Integrated Model (SWIM) was applied to the drainage area of the Mar Menor coastal lagoon, using a set of 15 climate scenarios and different land use maps and management settings. We assessed the long-term average seasonal and annual changes in generated runoff, groundwater recharge and actual evapotranspiration in the catchment, as well as on water inflow and nutrients input to the lagoon. The projected average annual changes in precipitation are small for the first scenario period, and so are the simulated impacts on all investigated components, on average. The negative trend of potential climate change impacts on water resources (i.e., decrease in all analyzed components) becomes pronounced in the second and third scenario periods. The applied socio-economic scenarios intensify, reduce or even reverse the climate-induced impacts, depending on the assumed land use and management changes.

Climate change is supposed to remarkably affect the water resources of coastal lagoons as they are highly vulnerable to changes occurring at their catchment and/or ocean or sea boundaries. Probable impacts of projected climate changes on catchment hydrology and freshwater input were assessed using the eco-hydrological model SWIM (Soil and Water Integrated Model) for the drainage areas of four European lagoons: Ria de Aveiro (Portugal), Mar Menor (Spain), Tyligulskyi Liman (Ukraine) and Vistula Lagoon (Poland/Russia) under a set of 15 climate scenarios covering the time period until the year 2100. Climate change signals for all regions show continuously increasing trends in temperature, but various trends in precipitation. Precipitation is projected to decrease in two catchments on the Iberian Peninsula and increase in the Baltic region catchment, and does not show a clear trend in the catchment located near the Black Sea. The average projected changes in freshwater inputs reflect these changes in climate conditions, but often show variability between the scenarios, in future periods, and within the catchments. According to the individual degrees of water management influences in the four drainage basins, the climate sensitivity of river inflows is differently pronounced in each.