Isotopic composition and hydrogeochemistry of a periglacial Andean catchment and its relevance in the knowledge of water resources in mountainous areas

ABSTRACT

Glacial and periglacial basins contain the largest reserves of fresh water in the world. These areas are extremely sensitive to global warming and climate change. The dry Andes of South America are characterized by large periglacial areas. This study focuses on the water isotopic composition and hydrochemistry of a typical periglacial environment of the Andes, in the Vallecitos catchment (2400–5500 m a.s.l.), Cordillera Frontal, Argentina. Detailed fieldwork was conducted between 2013 and 2017 with 240 samples collected for major ions and physicochemical parameters, and 67 samples analysed for ²H and ¹⁸O. The chemical composition of precipitation is typical Ca-HCO₃, while streams and groundwaters are Ca-MgSO₄ type. The isotope content of precipitation shows a wide dispersion. The snow samples are in general more depleted than the rainfall. Some springs vary their composition seasonally, associated to the melting of perennial snow patches. In general, all samples from the upper basin present depleted isotope contents related to recharge at higher altitudes, whereas samples from the lower basin show more enriched values. Intermediate compositions reflect the melting of snow and degrading ice-rich permafrost. These results will give a better understanding of the dynamics of water to manage water resources.

GRAPHICAL ABSTRACT

KEYWORDS:

• Andes
• Argentina
• groundwater
• hydrogen-2
• isotope hydrology
• oxygen-18
• permafrost
• snow

Acknowledgements

The authors acknowledge the National Atomic Energy Commission (CNEA) and IANIGLA Institute for Field and Laboratory Logistics. We thank INGEIS Laboratories for the isotope analysis, Lic. Ivanna Pecker Marcosig and Nicolás A. Taboada for help during sampling as well as the staff of UNCUYO and San Bernardo mountain shelters. We also would like to express special thanks to Talley Zabriskie for her review and comments.

Disclosure statement

No potential conflict of interest was reported by the author(s).