Origin of spring waters employing a multiparametric approach with special focus on stable isotopes ²H and ¹⁸O in the Lagoa Santa Karst region, Southern Brazil^*

* Originally presented at the IAEA Symposium on Isotope Hydrology 2019, Vienna, Austria, 20–24 May 2019.

ABSTRACT

Karst environments have an inherent complexity that interferes with their hydrogeology comprehension. Hence, isotope hydrology can be a valuable tool to assess trajectory of subsurface flows in an unexplored setting. The study area is located in the Lagoa Santa Karst, an environmental protection area of great economic, cultural and ecological importance, where Neoproterozoic metalimestones accommodate karst-fractured aquifers, characterized by complex water dynamics, essential vulnerability and high productivity. The purpose of this study was to investigate groundwater flow origins of springs using principally environmental stable isotopes ²H and ¹⁸O. Rainwater and spring water were sampled and analysed. The LMWL presents angular and linear coefficients strongly similar to those of the GMWL. Spring isotopic signatures, which represent the base flow and present wide-ranging of ²H and ¹⁸O, were separated into two groups. The first group can be associated with recent rainwater major contributions, while the second group shows significant evaporated water contributions, largely represented by resurgences. Tritium concentration and physico-chemical parameter data supported this interpretation, pointing that waters of the second group remained more time on the surface and subsurface. Therefore, using isotope tracers to evaluate upper groundwater zone in this tropical karst system is a powerful instrument for water resources management.

KEYWORDS:

• Hydrogen-2
• hydrogen-3
• isotope hydrology
• karst hydrogeology
• karst springs
• oxygen-18
• physico-chemical parameters
• recharge
• water resources management
• water–rock interaction

Acknowledgements

We appreciate the assistance provided by: The Geosciences Institute of Federal University of Minas Gerais (IGC-UFMG), The Nuclear Technology Development Center (CNEN/CDTN), The Geological Survey of Brazil (CPRM) and The Water Management Institute of the State of Minas Gerais (IGAM).

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Carolina Ribeiro http://orcid.org/0000-0002-6751-8635

Notes

* Originally presented at the IAEA Symposium on Isotope Hydrology 2019, Vienna, Austria, 20–24 May 2019.

Additional information

Funding

This work was supported by The National Center for Cave Research and Conservation (Centro Nacional de Pesquisa e Conservação de Cavernas, CECAV) through FUNDEP/GERDAU/UFMG Project n° 22.317; and by The Foundation for Research of the State of Minas Gerais (Fundação de Amparo à Pesquisa do Estado de Minas Gerais, FAPEMIG, grant IDs BPM and APQ 02049-14. This study was also financed in part by the Higher Education Personnel Improvement Coordination (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil, CAPES) - Finance Code 001.