Acuífero Guaraní (Formación Misiones)

The Guaraní Aquifer System extends beneath parts of Argentina, Brazil, Paraguay and Uruguay, covering about 1.2 million km² in total, of which about 71,740 km² are in Paraguay according to Wikipedia. The name was proposed by Uruguayan geologist Danilo Antón as a tribute to the Guaraní people. The reservoir is weakly cemented sandstone, laid down by rivers and dune deserts in the Triassic and Jurassic, and it goes by different names depending on the country: Botucatú in Brazil, Tacuarembó in Argentina and Uruguay, and Misiones in Paraguay.

Over much of eastern Paraguay it is covered by the basalts of the Alto Paraná Formation, which act as a low-permeability layer. Since it is not a karst aquifer, it is less vulnerable to contamination than limestone areas. Even so, it is a shared resource that deserves care.