Environmental Stable Isotope of the Sistema de las Encadenadas de Chascomús, Buenos Aires, Argentina

DAPEÑA, CRISTINA; MIRETZKY, PATRICIA; PANARELLO, HECTOR; FERNANDEZ CIRELLI, ALICIA

COMUNICACIONES - DEPARTAMENTO DE GEOLOGIA. FACULTAD DE CIENCIAS FISICAS Y MATEMATICAS. UNIVERSIDAD DE CHILE

Universidad de Chile

Lugar: Santiago, Chile; Año: 2001 vol. 52 p. 101 - 101

0069-357X

The Sistema de las Encadenadas de Chascomús (Salado River drainage basin) lies in the geomorphologic unit called Pampa Deprimida in the Buenos Aires province, Argentina. The Pampeano Plio-Pleistocene sediments contain the aquifer unit. This paper studies the relation between groundwater and surficial water by hydrochemistry and environmental stable isotopes (2H, 18-O). The hydrochemistry results suggest that during summer, when the precipitation-evaporation balance is negative, the evaporation process governs the surface water hydrochemistry, while appreciable differences between summer and winter groundwater values are not observed. The groundwater isotopic composition is relatively constant: -5.5? and 30? for d18-O and δ2H, respectively, indicating their meteoric origin. Nevertheless, small fluctuations are probably due to evaporation of local precipitation prior to infiltration. Recharge waters reflect the mean precipitation with reasonable fidelity. The stream and lake waters fit on an evaporation line (d18O=-5.5?, d2H=-30?), indicating the groundwater contribution.  The isotopic results suggest that during summer, the evaporation process governs the surface water hydrochemistry. The origin of groundwater is meteoric and the shallow groundwater constitutes the base flow of surficial water