Managing the effects of multiple stressors on aquatic ecosystems under water scarcity
GLOBAQUA Final Conference – 18-19 December 2018, Barcelona
Name: Stefano Mallucci Email: stefano.mallucci@unitn.it Institution: University of Trento Type (oral/poster) Oral and Poster
Water quality trends and drivers in European rivers
Elena Diamantini1, Stefanie R. Lutz2, Stefano Mallucci3, Bruno Majone4, Ralf Merz2, and Alberto Bellin4
1 Autonomous Province of Trento, Trento, Italy
2 UFZ Helmholtz Centre for Environmental Research, Department Catchment Hydrology, Halle (Saale), Germany 3 University of Trento / Fondazione Edmund Mach, Center Agriculture Food Environment, San Michele all'Adige, Italy
4 University of Trento, Department of Civil, Environmental and Mechanical Engineering, Trento, Italy
The ecological and chemical status of freshwater has recently attracted significant attention, since water bodies nurturing important ecosystems are subject to anthropogenic and climatic stressors often acting in synergy. However, the connection between water quality parameters and the main controlling factors has not been fully understood. In this study, thirteen physicochemical surficial water variables and four drivers (i.e. monthly aggregated air temperature and streamflow, population density and percentage of agricultural land use) were analysed in three large European river basins (i.e. Adige, Ebro, Sava). In particular, the purpose of the analysis is to identify how indicators of water quality and drivers of change coevolve in three large river basins representing the diversity of climatic, soil and water uses conditions observed in southern Europe. In addition, the complex interplay between water quality trends and the main drivers, observable at large scales and affecting surface water quality, were explored by analysing whether observed changes are consistent with the selected controlling factors. Advanced statistical analyses (i.e. Spearman rank correlation, principal component analysis, Mann-Kendall trend test and Sen’s Slope estimator) were performed in order to analyse long-term time series of water quality data during the period 1990-2015; to detect links between variables patterns and drivers; and to compare the river basins under investigation with respect to their vulnerability and resilience to the identified drivers of change.
Air temperature, considered as a proxy of climate change, shows a significant impact in all basins, particularly in the Adige and Ebro: positive trends of water temperature and negative for dissolved oxygen are correlated with upward trends of air temperatures. The aquatic ecosystems of these rivers are therefore experiencing a reduction in oxygen, which may further exacerbate in the future given the expected increase of temperature for this century. Furthermore, monthly streamflow reduced in the Ebro River, thereby decreasing the beneficial effect of dilution, as appears evident from the observed upward patterns of chloride concentration and electrical conductivity. Upward trends of chloride and biological oxygen demand in the Adige and Sava and positive trends of phosphate in the Adige are related to the increase of population and finally phosphates in the Sava and biological oxygen demand in the Ebro are highly correlated with agricultural land use. The study showed the complex relationships existing between drivers and observed changes in water quality parameters across three large European river basins and can represent a reliable tool for decision makers in river basin planning by providing an overview of the potential impacts of ongoing climatic changes or of particular policies on the aquatic ecosystem under investigation.
Acknowledgements
This research has been financially supported by the European Union 7th Framework Programme (Grant agreement no. 603629-ENV-2013-6.2.1-Globaqua).
References
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