Uso de herramientas hidroquímicas e isotópicas para evaluar el rol del agua subterránea en el funcionamiento hidrológico de una laguna Pampeana, provincia de Buenos Aires, Argentina

Abstract

Waters from the fractured-karstic and detritic (Pampeano) aquifers, and from surface water bodies are closely interacting in the Tapalqué Creek Upper Basin (CSAT for its acronym in Spanish), southeast of the Chaco-Pampean plain, Argentina. The La Barrancosa lake, endorheic and of socio-economic and cultural relevance, is located in this basin headwater. Within the framework of an integrated vision of these water resources, the main objective of this work is to know this lake’s water origin, as well as to identify and explain the processes involved in its interaction with the Pampeano aquifer. Hydrochemical and isotopic (δ2H and δ18O) tools were jointly used, with special emphasis on the ionic ratios study and the hydrochemical modelling. The rainwater evaporation during infiltration into aquifers and the dissolution/weathering of the geological materials rich in Ca2+, Mg2+ and K+ present in the study area, are the main processes that determine the composition of waters in the recharge zones. The dissolution of Na+-rich minerals and the cationic exchange are of relevance toward the plain zone. This last process and the concentration by evaporation control the composition of the La Barrancosa lake waters (effluent). These conclusions are validated by the δ2H, δ18O and d values characteristic of the CSAT waters and can be extrapolated to other basins developed in similar environments.