Characterization of anthropogenic impacts in Mediterranean intermittent rivers with chemical, ecological and hydrological indicators

Water scarcity in the Mediterranean area has increased the number of intermittent rivers, whose flow ceases either occasionally or totally. Key elements to characterize their dynamics are water quality, hydrological, and ecological status, when wastewater effluents dominate flow. Regarding water quality, pharmaceuticals are major pollutants, and serve as indicators of wastewater presence. Intermittent rivers are biodiversity hotspots where their hydrological regime may suffer alterations associated with wastewater effluents, making them harder to characterize than perennial streams. This study aimed to integratively characterize intermittent rivers through chemical, ecological and hydrological status calculating respective indices in twenty Mediterranean intermittent wastewater-impacted rivers located in Spain, France, Italy, Algeria and Tunisia. Pharmaceuticals were used as indicators assessing their frequency of PNEC exceedance and detection; while two ecological indicators and one hydrological indicator were used to evaluate wastewater stress on catchments. All indicators displayed a noticeable decline from upper to lower parts of the rivers, proving the effect of anthropogenic stressors on the aquatic environment. The Tunisian catchment displayed the most compromised conditions across all indicators, and the Algerian site even though low concentrations were detected, five compounds exceeded PNEC thresholds. This highlights the need for increased dedication and the adoption of water pollution solutions.