Determinación de la edad del agua en el acuifero pampeano en la cuenca del río Quequén Grande (Buenos Aires)

MARTINEZ, DANIEL E.; SOLOMON, KIP; DAPEÑA, CRISTINA; QUIROZ LONDOÑO, MAURICIO; MASSONE, HECTOR

Santa Rosa, La Pampa

Congreso; VI Congreso Argentino de Hidrogeología y IV Seminario Hispano-Latinoamericano sobre temas actuales de la Hidrología Subterránea; 2009

Asociacion Internacional de Hidrogeologos-Grupo Argentino AIH-GA y Facultad de Cs Exactas y Naturales UNLPam

Water age in an aquifer system can be defined as the elapsed time since the sample wasisolated from the atmosphere. Mean residence time is defined as the ratio between the totalwater volume and the groundwater outflow. Mean residence time of groundwater within anaquifer can potentially be estimated if water samples that represent a complete distribution offlow paths can be collected. Then, taking samples from gaining rivers and springs can resultin a good approximation to the problem. A sampling campaign for CFCs and 3H/3He wascarried out during May 2007, including even groundwater and surface water. Different typesof samplers were used as copper tubes and diffusion passive samplers. Noble gases andCFCs measurements were made at the laboratories of the University of Utah, and 3H weremade at the INGEIS laboratories. The obtained results by CFCs measurements indicate asrecharge years between 1948 and 1953 for groundwater samples, and between 1976 and1989 for streamwater. Apparent air equilibration has occurred for noble gases, giving tooyoung apparent ages. Integrated analysis of CFCs and noble gases information leads toconclude that apparent water ages ca. 50 years can be assigned to groundwater andbaseflow. According these results, a shallow groundwater zone of about 75 m is dischargingdirectly on streams, while a deeper groundwater zone is discharging directly to the ocean.