Mance et al. (2026) Stable Isotope Analysis of Precipitation—Karst Groundwater System (Mt. Učka, Croatia)

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Identification

• Journal: Water
• Year: 2026
• Date: 2026-01-25
• Authors: Diana Mance, Maja Radišić, Maja Oštrić, Davor Mance, Alenka Turković-Juričić, Ema Toplonjak, Josip Rubinić
• DOI: 10.3390/w18030308

Research Groups

Not specified in the provided text.

Short Summary

This study characterized precipitation-groundwater dynamics in the Mt. Učka karst system, Croatia, using multi-tracer approaches, revealing its dual porosity, vulnerability to contamination, and reliance on cold-season, high-elevation recharge.

Objective

• To characterize precipitation–groundwater dynamics in the Mt. Učka karst system (Croatia) by integrating stable isotope analysis, hydrochemistry, and hydrological time series.
• To demonstrate the necessity of multi-tracer approaches for comprehensive aquifer characterization.

Study Configuration

• Spatial Scale: Mt. Učka karst system, Croatia, covering an altitudinal gradient of approximately 1400 meters for precipitation sampling and including three major groundwater sources.
• Temporal Scale: 2.5 years.

Methodology and Data

• Models used: No specific hydrological or hydrogeological models were explicitly mentioned; the study primarily used analytical methods.
• Data sources: Precipitation samples collected across an altitudinal gradient, groundwater samples from three major sources, stable isotope data (δ2H, δ18O), hydrochemical data, and hydrological time series.

Main Results

• Precipitation exhibits significant isotopic variability, with d-excess values indicating mixed Atlantic–Mediterranean moisture sources.
• Groundwater is primarily recharged by precipitation from the cold part of the hydrological year.
• Groundwater shows substantial attenuation of isotopic signals, indicating extensive mixing processes, which prevented quantitative estimation of mean residence time.
• Groundwater is predominantly recharged from elevations above 900 meters above sea level (m a.s.l.), with one spring showing evidence of even higher-elevation recharge.
• The system exhibits dual porosity: a rapid, conduit-dominated response indicates high vulnerability to surface contamination, while a sustained, matrix-dominated response provides greater buffering capacity.
• The findings highlight the vulnerability of karst systems to projected reductions in autumn precipitation, identified as a critical recharge season.

Contributions

• Provides a comprehensive characterization of precipitation-groundwater dynamics, recharge sources, and vulnerability of the Mt. Učka karst system using a multi-tracer approach.
• Demonstrates the critical importance of multi-tracer approaches for understanding complex karst aquifer systems.
• Highlights the specific vulnerability of Mediterranean karst systems to climate change, particularly reductions in autumn precipitation.

Funding

Not specified in the provided text.

Citation

@article{Mance2026Stable,
  author = {Mance, Diana and Mance, Diana and Radišić, Maja and Oštrić, Maja and Mance, Davor and Mance, Davor and Turković-Juričić, Alenka and Toplonjak, Ema and Rubinić, Josip},
  title = {Stable Isotope Analysis of Precipitation—Karst Groundwater System (Mt. Učka, Croatia)},
  journal = {Water},
  year = {2026},
  doi = {10.3390/w18030308},
  url = {https://doi.org/10.3390/w18030308}
}