Hydrogeochemical and isotopic tools to study groundwater flow in low gradient catchments. Study cases in the province of Buenos Aires, Argentina.

QUIROZ LONDOÑO, MAURICIO; MARTINEZ, DANIEL E.; DAPEÑA, CRISTINA; MASSONE, HÉCTOR

HYDROGEOLOGY JOURNAL

Springer Verlag

Año: 2008 vol. 16 p. 1113 - 1127

1431-2174

The region known as Pampa Plain, in Argentina, is a vast area characterized by slopes of less than 0.05%. The surface sediment is silty sand, mainly Aeolian, referred to as Pampean Loess, which is a phreatic aquifer unit of utmost importance for the water supply of the region. On account of the slight gradient, hydrogeological analyses using only hydraulic measurements are dif.cult to perform, often leading to confusing results. Thus, the study presented relies on hydrochemical modeling and isotopic determinations as well. The study area comprises three catchments in the inter-mountainous area corresponding to El Moro, Tamangueyú and Seco creeks, and covering 2,570 km2 in the province of Buenos Aires. Measurements of piezometric levels and samples of groundwater, surface water and rainwater were carried out between January and March 2005. Major ion results were analyzed by means of hydrochemical graphs and hydrogeochemical modelling using NETPATH. The resulting data show that it is possible to identify local changes in recharge, .ow direction and stream/groundwater relationship relationship by using hydrochemical and isotopic information, which may become a useful and more precise tool for the study of particularly .at landscapes.