THE GUARANI AQUIFER SYSTEM: A RESOURCE SHARED BY FOUR COUNTRIES

The Guaraní Aquifer System (SAG) is one of the world´s most important fresh groundwater reservoirs, due to its extension (1,200,000 km2) and its volume (40,000 km3). The SAG is shared by four countries: Argentina, Brazil, Paraguay and Uruguay (South America), which use this resource for various purposes with different exploitation levels.

The research activities carried out in each country by scientists coming from different disciplines and institutions allowed to define the main characteristics of this aquifer system briefly described here. This mega - aquifer is contained in aeolian and fluvial sands from the Triassic - Jurassic, usually covered by basalt formations from the Cretaceous, which provide a high confinement degree. The pattern of this sandy sediments is due to: the Paraná Sedimentary Basin boundaries, the faults, the structural features and the basalt deposits that cover the sandstones. Its thickness ranges from 50 up to 800 m. The deepness varies and reaches up to 1,800 m. Other distinctive characteristics are its high pressures and artesian yields at certain locations of the basin, the low salinity of its waters and its temperature. The last one, by geothermical gradient is between 38 and 85 oC. These results, the aquifer exploitation levels, as well as the need of proper hydrogeological data, integrated management guidelines and international legislation are key aspects to be discussed taking into account that these points are essential toward achieving the sustainable use and the preservation of this shared resource which with its estimated storage volume could supply the current world population (5,500 million) during 200 years, at a rate of 100 liters per day per inhabitant.