Geohydrology

Abstract

The state-of-the-art hydrogeological research , the chronology of studies on the subject, and the conformation of the physical component of the geohydrological system are analyzed. Two units are observed: the upper (SGS) and lower geohydrological system (SGI) , from the Salamanca Formation to the surface. In the SGS the main aquifers occur (Patagonia and Santa Cruz formations), generically called Patagonian aquifer . They may be phreatic or semi-confined , with marked anisotropy and heterogeneity , an 8–15 m³/h yield, specific yields of 100–150 m³/d m, and a transmissivity of over 80 m²/d. The vadose zone reaches thicknesses of over 20 m in tableland areas. The geohydrological cycle is described. Recharge may be direct autochthonous , indirect autochthonous , or allochthonous . Circulation was interpreted by making an equipotential diagram: the general flow direction is towards the east. The is 1.4–1.6 × 10⁻² and the effective velocity , 2.55 × 10⁻² to 2.25 × 10⁻¹ m/d. Regional discharge occurs to the ocean, the consumptive use is very limited as xerophytic vegetation prevails, and a specific case involves springs. In the hydrochemical analysis , difficulties arose due to the anisotropy and heterogeneity, and to the level, density, and detail of the information available. SGI aquifers have higher salinity and sodium chloride type water. In the SGS, water in the Patagonia Formation has low TDS, mainly of sodium chloride and/or sodium sulphate type, and some of sodium bicarbonate type. Water in the Santa Cruz Formation has very low TDS, is of sodium chloride and/or sodium sulphate type, or sodium bicarbonate type.