MODELO HIDROGEOQUÍMICO E ISOTÓPICO DE ACUÍFEROS CONFINADOS. CÓRDOBA. ARGENTINA

CABRERA, ADRIANA; DAPEÑA, CRISTINA; BLARASIN, MONICA; PANARELLO, HECTOR; MATTEODA, EDEL

Quito, Ecuador

Congreso; IX Congreso Latinoamericano de Hidrología Subterránea; 2008

ALHSUD, EMAAP, GECAIH, CIGMYP (Ecuador) y Alcadía Metropolitana de Quito

The objective of this work is to present a preliminary hydrogeochemical and isotopic model ofconfined deep aquifers in the studied area, resources of greatest interest due to the badquality of the unconfined aquifer. Conventional methodologies were used and hydrochemicalmaps, Schoeller diagrams, box plots and dendrograms (Q mode) were obtained. Theisotopic analysis (18O and 2H) were very significant in the assessment of these deep aquiferssince the few sedimentological and hydraulic data of the deepest layers made difficult ahydrogeologic classification. The deepest sediments (120 m to 350 m), fluvial materials withwide-ranging texture, were assigned to Upper Tertiary units. Three deep multilayered aquifersystems were defined taking into account depths and groundwater quality: a semiconfinedsystem (SAS), a confined system with low confinement grade (SCA) and a confined systemwith high confinement grade (SCB). Although all of them contain fresh waters (CE < 2,800μS/cm), hypothermal and mesothermal (29ºC -36ºC) and sodium sulphate geochemical type,the SAS (120 m-200 m) and SCA (225-290 m) levels displayed the most saline waters (CE >1,800 μS/cm) and the greatest concentrations of As and F- and similar isotopic content to thephreatic system (δ18O = -5.0? a -4.6? y δ2H = -32? a -28?), being able to suppose afeasible hydraulic connection between these aquifers. The isotopic composition of local andwestern allochthonous streams and the characteristics of deepest confined levels (SCB, 225-340 m), with always artesian wells, better groundwater quality (CE < 1,800 μS/cm) anddifferent isotopic composition (δ18O≈-6,6?;δ2H≈-43?) allow us to assume recharge sectorslocated outside this area, in the western perimountain region.