Río de la Plata: An Estuary and Basin, Not a River

The Río de la Plata (River of Silver) is not a river in the conventional sense. It is a vast, funnel-shaped estuary formed by the confluence of the Paraná River and the Uruguay River, on the border between Argentina and Uruguay. It extends ~290 km (180 mi) from the confluence to the Atlantic Ocean, widening from ~48 km to ~220 km at its mouth. The Río de la Plata Basin (3.2 million km²) is South America's second-largest drainage system, covering parts of Brazil, Argentina, Paraguay, Bolivia, and Uruguay. The estuary itself is a highly productive, sediment-rich mixing zone, home to the Port of Buenos Aires and Montevideo. Its "length" is not defined as for a river; rather, its extent is described by its geometry and the length of its feeder rivers (Paraná: ~4,880 km; Uruguay: ~1,838 km).