title: Hydroclimatic and water quality trends across three Mediterranean river basins.
abstract: Water resources are under pressure from multiple anthropogenic stressors such as changing climate, agriculture and water abstraction. This holds, in particular, for the Mediterranean region, where substantial changes in climate are expected throughout the 21st century. Nonetheless, little attention has been paid to linkages between long-term trends in climate, streamflow and water quality in Mediterranean river basins. In the present study, we perform a comparative analysis of recent trends in hydroclimatic parameters and nitrate pollution in three climatologically different Mediterranean watersheds (i.e., the Adige, Ebro and Sava River Basins). Mann-Kendall trend analyses of annual mean temperature, precipitation and streamflow (period 1971 to 2010) and monthly nitrate concentrations, mass fluxes and flow-adjusted concentrations (period 1996 to 2012) were performed in these river basins. Temperature is shown to have increased the most in the Ebro followed by the Sava, whereas minor increases are observed in the Adige. Precipitation presents, overall, a negative trend in the Ebro and a positive trend in both the Adige and Sava. These climatic trends thus suggest the highest risk of increasing water scarcity for the Ebro and the lowest risk for the Adige. This is confirmed by trend analyses of streamflow time series, which indicate a severe decline in streamflow for the Ebro and a substantial decline in the Sava, as opposed to the Adige showing no prevailing trend. Concerning surface water quality, nitrate pollution appears to have decreased in all study basins. Overall, these findings emphasize progressive reduction of water resources availability in river basins characterized by continental climate (i.e., Ebro and Sava). This study thus underlines the need for adapted river management in the Mediterranean region, particularly considering strong feedbacks between hydroclimatic trends, freshwater ecosystem services and water resources availability for agriculture, water supply and hydropower generation.
authors.affiliation: UFZ Helmholtz Centre for Environmental Research, Department Catchment Hydrology, Theodor-Lieser-Str. 4, 06120 Halle (Saale), Germany. Electronic address: stefanie.lutz@ufz.de.
authors.forename: Stefanie R
authors.initials: SR
authors.lastname: Lutz
authors.affiliation: University of Trento, Department of Civil, Environmental and Mechanical Engineering, Via Mesiano 77, 38123 Trento, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Mallucci
authors.affiliation: University of Trento, Department of Civil, Environmental and Mechanical Engineering, Via Mesiano 77, 38123 Trento, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Diamantini
authors.affiliation: University of Trento, Department of Civil, Environmental and Mechanical Engineering, Via Mesiano 77, 38123 Trento, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Majone
authors.affiliation: University of Trento, Department of Civil, Environmental and Mechanical Engineering, Via Mesiano 77, 38123 Trento, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Bellin
authors.affiliation: UFZ Helmholtz Centre for Environmental Research, Department Catchment Hydrology, Theodor-Lieser-Str. 4, 06120 Halle (Saale), Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Merz
mesh_terms: D002980:Climate; D004784:Environmental Monitoring; D005060:Europe; D062070:Hydrology; D009566:Nitrates / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality
chemical_list: D009566:Nitrates; D014874:Water Pollutants, Chemical
keywords: Hydroclimatic trends; Mann-Kendall trend analysis; Mediterranean river basins; Nitrate pollution trends; Streamflow; Water scarcity