Guaraní Aquifer System

The Guaraní Aquifer System (GAS) is a large underground groundwater reservoir and hydrogeological system. It is a transboundary aquifer spread across four South American countries: Argentina, Brazil, Paraguay, and Uruguay.

The aquifer was named in honor of the Guaraní peoples, who occupied a large part of the aquifer system territory until the arrival of the European settlers in the 16th century.

With a thickness of 50 - 600 m (165 - 2,000 ft) and averaging about 250 m (800 ft), the Guaraní is one of the world's largest sandstone aquifers.

The aquifer system covers approximately 1,200,00 sq km (463,300 sq mi) in northeastern Argentina, southern Brazil, southeastern Paraguay, and northern Uruguay.

Approximately seventy percent of the area occupied by the aquifer is located in the subsoil of south-central Brazil; the remaining 19% is in Argentina, 6% in Paraguay, and 5% in Uruguay.

The Guaraní Aquifer lies under six South American rivers:

• the Paraná River (Argentina, Brazil, and Paraguay)

• the Paraguay River (Argentina, Brazil, and Paraguay)

• the Uruguay River (Argentina, Brazil, and Paraguay)

• the Bermejo River (Argentina)

• the Salado River (Argentina)

• the Pilcomayo River (Argentina and Paraguay)

The aquifer is best known and most exploited in Brazil's São Paulo State, at 80% of its current total extraction rate.

Approximately 24 million people live in the area delimited by the boundaries of the aquifer, and a total of 70 million people live in areas that directly or indirectly influenced it.

The primary use of the aquifer is for drinking water supply, but there are also industrial, agricultural irrigation, and thermal tourism uses.

Geology

The Guaraní Aquifer consists primarily of fluvial and aeolian sandstones of the Piramboia and Botucatu sedimentary geological formations, which were deposited during the Triassic and Jurassic periods.

_{Topographic map depicting the location of the Guaraní Aquifer}