Caracterización hidroquímica e isotópica de las aguas subterráneas de la ciudad de Gualeguaychú. Entre Ríos. Argentina

BOUJON, PAMELA; SANCI, ROMINA; STÖCKLI, FERNANDO; DAPEÑA, CRISTINA

ASUNCIÓN, PARAGUAY

Congreso; VIII Congreso Latinoamericano de Hidrología Subterránea.; 2006

ASOCIACIÓN LATINOAMERICANA DE HIDROLOGÍA SUBTERRANEA PARA EL DESARROLO (ALHSUD)

Gualeguaychú city is located in the south eastern of the Entre Ríos province, (33º00’36.9’’de LS y 58º30’40’’LO), near the confluence of Gualeguaychú river and Uruguay river. This Gualeguaychú river basin is in a softly plain with two negative geoforms (Uruguay and Gualeguaychú river) which constituted the preferential groundwater discharge zone, for phreatic water and the semiconfine aquifer, and another positive geoform, named Cuchilla Grande, which acts like a divisor for groundwater and superficial waters. VIII Congreso Latinoamericano de Hidrología Subterránea – Septiembre, 2006- Asunción, Paraguay Climate is characterized by 1077 mm annual average precipitation and annual average temperature of 17.6 Cº for 1969/2005. River water constitutes the main water supply for human consume at the city. Groundwater extraction is an alternative for some areas affected by low water pressure and is mixed with river water and then injected to the municipal company network. It is important to point out that the wells are old and built with scarce technology. Besides they are probably affected by reflux and mixtures between water supply and wells. This work presents the preliminary chemical and isotopic results to characterize groundwater. Likewise, the flow direction was determined and the relationship between groundwater and superficial water. Precipitation record from the Gualeguaychú station which belongs to the Red Nacional de Colectores de Argentina and Global Network for Isotopes in Precipitation was used to evaluate the input . This station operates since June, 2004. During December, 2005 and April, 2006 two sampling were performed and 24 wells from Gualeguaychú city and surroundings were checked. Major chemical analyses and isotopic measurements (2H y 18O).were done at INGEIS’ Laboratories Preliminary groundwater characterization was made and was classified into six groups: bicarbonate sodium type water, bicarbonate calcium type water, sulfate sodium type water, sulfate sodium type water, sulfate calcium type water, chloride calcium type water and chloride sodium type water. Groundwater isotope composition has meteoric origin and shows some variability. These variations may be due to evaporation prior infiltration, selective recharge and mixing mechanisms.