Stable isotope studies applied to hydrogeology in the periglacial environment of the central Andes of Mendoza, Argentina

SILEO, NOELIA R.; DAPEÑA, CRISTINA; TROMBOTTO LIAUDAT DARÍO; PECKER MARCOSIG, IVANNA

San Luis

Workshop; I Regional Workshop on Isotope Ecohydrology; 2020

Grupo de Estudios Ambientales, IMASL (CONICET - UNSL)

Glacial and periglacial basins contain most of fresh water reserves in the world. In a global warming context these areas are the most sensitive. The dry Andes of South America are characterized by these large periglacial areas. Our study focuses on the water isotopic composition and hydrochemistry of a typical periglacial environment of the Andes, in the Vallecitos catchment (2400-5500m asl), Cordillera Frontal, Argentina. A detailed fieldwork was carried out between 2013- 2017 where over 100 samples were analyzed for 2H and 18O besides physico-chemical parameters (pH, TDS, CE, DO) and major ions. The chemical composition of precipitation is typical CaHCO , while 3streams and groundwaters are Ca-MgSO type, showing a strong relationship with geology. The isotopic content of 4precipitation shows a wide dispersion. The snow samples are in general more depleted than the rainfall. Some springs vary its composition seasonally, indicating also an association to perennial snow patches fusion. In general, all samples from the upper basin present depleted isotopic contents associated with recharge at higher altitudes, whereas samples from the lower basin show more enriched values. Intermediate compositions indicate in many cases the contribution from fusion processes of snow and permafrost degradation. Results presented will give a better understanding of the situation on water resources from these sensitive zones