Markogianni et al. (2026) Watershed Dynamics in the Prespa Lakes: An Integrated Assessment of Stream Inflow Effects

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Identification

• Journal: Water
• Year: 2026
• Date: 2026-02-22
• Authors: Vassiliki Markogianni, Ioanna Zotou, Evangelia Smeti, Anastasia Lampou, Ioannis Matiatos, Ioannis Karaouzas, Elias Dimitriou
• DOI: 10.3390/w18040518

Research Groups

Not explicitly mentioned in the provided text.

Short Summary

This study investigated the ecological and hydrological impacts of stream inflows on the Greek part of the Prespa Lakes system, revealing distinct drivers for water storage variability in each lake and highlighting the influence of anthropogenic pressures on stream ecological status and lake water quality, necessitating cross-border management.

Objective

• To identify the ecological and hydrological impacts of contributing stream inflows on the Greek part of the Prespa Lakes system by examining spatial variability in physicochemical and biological conditions, conducting water balance analyses, and performing isotopic analyses.

Study Configuration

• Spatial Scale: Greek part of the Prespa Lakes system, including Lesser Prespa Lake, Great Prespa Lake, and their contributing streams (e.g., Agios Germanos River catchment).
• Temporal Scale: Multi-year, with seasonal and annual analyses, including observations of long-term water level decline and monthly nutrient load impacts.

Methodology and Data

• Models used: Water balance analysis, correlation analysis.
• Data sources: In-situ physicochemical and biological measurements, isotopic analyses (δ18O, δ2H), field data.

Main Results

• Streams draining into Lesser Prespa Lake exhibited more pronounced hydrological and physicochemical fluctuations compared to the Agios Germanos River connected to Great Prespa Lake.
• Ecological status classifications of all studied streams ranged from high to moderate, with moderate conditions (especially downstream) closely associated with anthropogenic pressures such as agricultural drainage, livestock activities, irrigated croplands, and wastewater discharges.
• Both lakes were classified as mesotrophic, but Lesser Prespa showed greater transparency loss than Great Prespa Lake.
• Nutrient loads from streams influenced Lesser Prespa Lake's nutrient concentrations with a lag of approximately one month; total nitrogen showed a moderate stream–lake correlation (R = 0.61), while total phosphorus exhibited a strong negative correlation (R = −0.94), suggesting substantial nutrient retention within the lake.
• Water balance analysis indicated an annual water deficit for both Lesser and Great Prespa Lakes, with Great Prespa experiencing a markedly stronger and systematic long-term decline in water level.
• Seasonal fluctuations in Lesser Prespa Lake's water volume were primarily driven by excess rainfall, with minimal contribution from stream inflows.
• For Great Prespa Lake, surface inflow from the Agios Germanos catchment was identified as the dominant driver of water storage variability, surpassing direct rainfall, with strong correlations in both wet (R = 0.79) and dry (R = 0.88) periods.
• Isotopic compositions (δ18O, δ2H) did not differ significantly between the two lakes, indicating common recharge sources and strong evaporative imprints, while stream isotopic signatures highlighted spatial and seasonal variability in hydrological inputs.
• Seasonal and spatial variations were strongly influenced by both natural hydrological dynamics and anthropogenic pressures within the basin.

Contributions

• Provides a comprehensive assessment of ecological and hydrological impacts of stream inflows on a transboundary lake system, integrating physicochemical, biological, water balance, and isotopic analyses.
• Quantifies the distinct drivers of water storage variability for two interconnected lakes within the same basin.
• Highlights the specific influence of anthropogenic pressures on stream ecological status and lake water quality, including nutrient dynamics and retention processes.
• Reinforces the critical importance of adopting holistic, cross-border management strategies for maintaining the ecological integrity and long-term sustainability of transboundary freshwater ecosystems.

Funding

Not explicitly mentioned in the provided text.

Citation

@article{Markogianni2026Watershed,
  author = {Markogianni, Vassiliki and Zotou, Ioanna and Smeti, Evangelia and Lampou, Anastasia and Matiatos, Ioannis and Karaouzas, Ioannis and Dimitriou, Elias},
  title = {Watershed Dynamics in the Prespa Lakes: An Integrated Assessment of Stream Inflow Effects},
  journal = {Water},
  year = {2026},
  doi = {10.3390/w18040518},
  url = {https://doi.org/10.3390/w18040518}
}