Relationships between geomorphological features and groundwater geochemistry in the upper and middle basin of Las Peñas stream, Pampean Mountains, Córdoba. Argentina

Abstract

Las Peñas stream basin, located in the Pampean Mountains of Cordoba (Argentina), has specific groundwater features which are of great interest for the local socioeconomic activities. The objective of this work is to define the geomorphological characteristics of the basin and interpret their influence on hydrogeological processes, emphasizing hydrodynamic and hydrogeochemical aspects. Groundwater flow in the unconfined aquifer has developed in both sediments and fractured rocks. The groundwater is fresh with electrical conductivities between 586 µS/cm and 2000 µS/cm, although there are localized samples in the piedmont of brackish type (up to 3900 µS/cm). Sampled groundwaters are almost entirely of calcium and sodium bicarbonate geochemical type, with local occurrence of mixed type (sodium-calcium bicarbonate and sodium bicarbonate-sulfate) waters. Taking into account geomorphological and lithological features, both groundwater flow and hydrochemical aspects are linked with the main geomorphological environments: a relict paleosurface with a sedimentary cover, a rocky dissected paleosurface with filled valleys and the sedimentary piedmont. It was interpreted that groundwater geochemistry is mainly linked to input from precipitation and weathering of silicates. Dissolution of carbonates and cation exchange processes contribute to the observed groundwater chemistry especially in the relict paleosurface and piedmont.