CONICET | Buscador de Institutos y Recursos Humanos

In this work an isotopic characterization of groundwater is presented in the northeast of La Pampa province, Argentina. This area is within the domain of two water regions: the eastern plain region (R1) and the central pampean plain region (R2). To carry out this characterization, the isotopic composition of precipitation was previously considered in monthly samples of rainfall collected at the stations of Intendente Alvear and Quemú Quemú, and a preliminary regional meteoric line was prepared. On the other hand, 41 public supply wells from 21 locations were sampled. Groundwater is predominantly bicarbonate sodium inR1 and chlorinated/sulfated sodium in R2. The isotopic composition of the groundwater in both regions has an average value of δ18O = -5.5 ?, δ2H = -32 ? and d = 12 ?, while the isotopic composition varied between -6,4 ? and -4,3 ? for δ18O and between -36 ? and -24 ? for δ2H. In both regions the variations found in the isotopic composition respond to the variations registered in the composition of the precipitation. The main processes correspond to previous modifications to the infiltration due to evaporation and selective infiltrationprocesses. Likewise, two salinization mechanisms have been identified: salt dissolution by transit where the isotopic composition does not change and evaporation processes that result in isotopic enrichment with an increase in chloride concentration.