Sepp et al. (2025) Impacts of climate change on the dilution capacity of perennial and non-perennial European rivers

Identification

• Journal: Water Research
• Year: 2025
• Date: 2025-08-27
• Authors: Margot Sepp, Mahdi Abbasi, Petra Döll, Anna Freixa, Rafael Marcé, Sergi Sabater
• DOI: 10.1016/j.watres.2025.124499

Research Groups

• Catalan Institute for Water Research (ICRA), Girona, Spain
• Institute of Physical Geography, Goethe University Frankfurt, Frankfurt/Main, Germany
• Senckenberg Leibniz Biodiversity and Climate Research Centre (SBiK-F) Frankfurt, Frankfurt/Main, Germany
• Centre d’Estudis Avançats de Blanes (CEAB), Consejo Superior de Investigaciones Científicas (CSIC), Blanes, Spain
• Institute of Aquatic Ecology (IEA), Universitat de Girona (UdG), Girona, Spain

Short Summary

This study evaluates the current and future capacity of perennial and non-perennial European river reaches to dilute wastewater treatment plant (WWTP) effluents under climate change. It reveals that non-perennial reaches have significantly lower dilution capacity, which is projected to decrease further in two-thirds of reaches under a high emissions scenario, particularly in vulnerable Mediterranean and semi-arid regions.

Objective

• To evaluate the actual and future capacity of perennial and non-perennial river reaches in Europe to dilute wastewater treatment plant (WWTP) effluents, considering average and extreme streamflow conditions under different climate change scenarios.

Study Configuration

• Spatial Scale: European river network.
• Temporal Scale: Reference period (1985–2014) and future period (2071–2100).

Methodology and Data

• Models used: Climate models and hydrological models (specific names not provided in the excerpt) were used to project future climatic conditions and high-resolution streamflow.
• Data sources: High-resolution streamflow data, cumulated upstream WWTP discharge data, and climate change scenarios (Representative Concentration Pathways RCP2.6 and RCP8.5).

Main Results

• Under reference conditions, the annual dilution factor (DF) was, on average, 4.6 times lower in non-perennial than in perennial reaches, with this difference increasing up to 10.8 times lower in August.
• Under the high emissions scenario (RCP8.5), the annual DF is projected to decrease significantly in two-thirds of the river reaches.
• River reaches in the Mediterranean and semi-arid regions of Europe exhibit low dilution capacity and are identified as the most vulnerable to WWTP discharges and climate change-induced streamflow reductions.
• In contrast, under the low emissions scenario (RCP2.6), the dilution factor is projected to remain largely unchanged.

Contributions

• Provides the first large-scale analysis of river dilution capacity that explicitly differentiates between perennial and non-perennial river reaches in Europe, addressing a critical gap given that over half of global river reaches are non-perennial.
• Quantifies the impact of climate change on a crucial ecosystem service (water purification) across Europe, highlighting regional vulnerabilities and the importance of emissions reductions.

Funding

• Not available in the provided text.

Citation

@article{Sepp2025Impacts,
  author = {Sepp, Margot and Abbasi, Mahdi and Döll, Petra and Freixa, Anna and Marcé, Rafael and Sabater, Sergi},
  title = {Impacts of climate change on the dilution capacity of perennial and non-perennial European rivers},
  journal = {Water Research},
  year = {2025},
  doi = {10.1016/j.watres.2025.124499},
  url = {https://doi.org/10.1016/j.watres.2025.124499}
}