Tziritis et al. (2026) Nitrate persistence and inland salinisation in an intensively irrigated Mediterranean river basin district: Diagnostic evidence from WFD monitoring data (Thessaly, central Greece)

Identification

• Journal: Journal of Hydrology
• Year: 2026
• Date: 2026-07-30
• Authors: Evangelos P. Tziritis, Dimitra Siakka, Vasilios Pisinaras
• DOI: 10.1016/j.jhydrol.2026.136130

Research Groups

• Hellenic Agricultural Organisation–Dimitra (ELGO-DIMITRA), Soil and Water Resources Institute (SWRI)
• School of Geology, Aristotle University of Thessaloniki (AUTh)

Short Summary

This study develops a probabilistic diagnostic framework to characterise the spatial extent and temporal persistence of nitrate contamination in the Thessaly River Basin District, central Greece. The framework advances beyond conventional descriptive assessments through three specific analytical contributions: bootstrap exceedance analysis, Shannon entropy-weighted Compound Vulnerability Index, and classification concordance analysis.

Objective

• Characterise the spatial extent and temporal persistence of nitrate contamination and quantify exceedance probabilities at the station level.
• Identify the dominant mechanisms of secondary ionic enrichment and assess the spatial relationship between salinisation and nitrate-impacted zones.
• Construct an integrated, entropy-weighted vulnerability metric that incorporates both chemical and hydraulic indicators.
• Evaluate the degree to which the official water body status classification captures the station-level contamination footprint.

Study Configuration

• Spatial Scale: River Basin District (RBD EL08) in central Greece, with 98 monitoring stations across a contiguous five-year monitoring cycle from 2019 to 2023.
• Temporal Scale: Five years of monitoring data, with annual arithmetic means and multi-year medians used for analysis.

Methodology and Data

• Models used: Bootstrap exceedance analysis, Shannon entropy-weighted Compound Vulnerability Index, and classification concordance analysis.
• Data sources: WFD groundwater monitoring data from the National Groundwater Monitoring Programme of Greece, accessed through the Water Information System for Europe (WISE).

Main Results

• Nitrate concentrations ranged from below detection to 296 mg/L, with a basin-wide multi-year median of 13.7 mg/L and a mean of 27.3 mg/L.
• 15.3% of stations maintained persistent contamination above 50 mg/L, while 28.6% maintained persistent contamination above 25 mg/L.
• Episodic exceedances of 50 mg/L and 25 mg/L were documented at 35 (35.7%) and 57 (58.2%) wells, respectively.

Contributions

• The study advances beyond conventional descriptive assessments through the use of probabilistic diagnostic methods, providing a more nuanced characterisation of contamination risk.
• The framework recovers a station-scale contamination footprint that body-level classification averages away, highlighting the importance of spatially explicit diagnostics in river basin management.

Funding

• This research was funded by [insert funding sources and project codes].

Citation

@article{Tziritis2026Nitrate,
  author = {Tziritis, Evangelos P. and Siakka, Dimitra and Pisinaras, Vasilios},
  title = {Nitrate persistence and inland salinisation in an intensively irrigated Mediterranean river basin district: Diagnostic evidence from WFD monitoring data (Thessaly, central Greece)},
  journal = {Journal of Hydrology},
  year = {2026},
  doi = {10.1016/j.jhydrol.2026.136130},
  url = {https://doi.org/10.1016/j.jhydrol.2026.136130}
}