Río de la Plata Basin

The Río de la Plata basin (Spanish: Cuenca del Plata, Portuguese: Bacia do Prata), more often called the River Plate basin in scholarly writings, sometimes called the Platine basin or Platine region, is the 3,170,000-square-kilometre (1,220,000 sq mi) hydrographical area in South America that drains to the Río de la Plata. It includes areas of southeastern Bolivia, southern and central Brazil, the entire country of Paraguay, most of Uruguay, and northern Argentina. Making up about one fourth of the continent's surface, it is the second largest drainage basin in South America (after the Amazon basin) and one of the largest in the world.

The main rivers of the La Plata basin are the Paraná River, the Paraguay River (the Paraná's main tributary), and the Uruguay River.

The La Plata basin is bounded by the Brazilian Highlands to the north, the Andes Mountains to the west, and Patagonia to the south. The watershed extends mostly northward from the source of the Río de la Plata for roughly 2,400 kilometres (1,500 mi), as far as Brasília and Cuiabá in Brazil and Sucre in Bolivia, spanning latitudes between 14 and 37 degrees south and longitudes between 43 and 67 degrees west. The Paraná River, La Plata's largest tributary, is South America's second longest river and one of the longest in the world.

Politically, the basin includes part or all of the Brazilian states of Mato Grosso, Goiás, Minas Gerais, São Paulo, Mato Grosso do Sul, Paraná, Santa Catarina, and Rio Grande do Sul; the Bolivian departments of Santa Cruz, Chuquisaca and Tarija; the entire country of Paraguay; the western and central departments of Uruguay; and the Argentine provinces of Jujuy, Salta, Formosa, Chaco, Misiones, Tucumán, Santiago del Estero, Santa Fe, Corrientes, Córdoba, Entre Ríos, Buenos Aires, and La Pampa.

The precipitation falling within this area is collected by numerous rivers to finally reach the Río de la Plata, almost all of it through the Paraná River, the Paraguay River, and the Uruguay River, La Plata's most important tributaries. The river discharges water into the Atlantic Ocean at an average rate of 22,000 cubic metres per second (780,000 cu ft/s), the majority of which comes from the Paraná.

The basin serves as the recharge zone for the Guarani Aquifer, one of the world's largest aquifer systems. The rivers of the La Plata Basin carry an estimated 57,000,000 cubic metres (2.0×10⁹ cu ft) of silt into the Río de la Plata each year, where the muddy waters are stirred up by winds and tides; the shipping route from the Atlantic to Buenos Aires is kept open by continual dredging.

The Paraná River's main tributaries include the Paranaíba River, Grande River, Tietê River, Paranapanema River, Iguazu River, Paraguay River, and the Salado River, after which it ends in the large Paraná Delta. The Paraguay River flows through the Pantanal wetland, after which its main tributaries include the Pilcomayo River and the Bermejo River, before it ends in the Paraná. The Uruguay's main tributaries include the Pelotas River, Canoas River, Ibicuí River, and the Río Negro. Another significant tributary to the Río de la Plata is the Salado del Sur River.

The Río de la Plata Basin has been the site of much conflict in the modern history of South America, much of it because the basin contained the (contested) frontiers between the Portuguese and Spanish Empires in South America and their successor states. A series of wars has been fought over territorial control in the region, particularly in the nineteenth century.