Abstract
The Guarani Aquifer System (GAS) is a large transboundary groundwater reservoir, located in the central-eastern region of South America. GAS is shared among Brazil, Argentina, Paraguay and Uruguay, and comprises an area of 1,200,000 km2, from which approximately 70% is in Brazilian territory. In the southwest region of the state of Rio Grande do Sul, GAS corresponds to a recharge zone, an…