Rio de la Plata (La Plata River) and Estuary (Argentina and Uruguay)

Abstract

The La Plata River system can be defined as a funnel coastal plain tidal river with a semi-closed shelf at the mouth. La Plata River is both the world’s widest freshwater system and an estuary that drains the second largest basin in South America and the fifth largest in the world. The Rio de la Plata system is shared by Argentina and Uruguay and has an area of 38,000 km², extends almost 300 km in length, and widens from about 40 km at the inner freshwater part to 227 km at the Atlantic Ocean boundary. The system is mainly formed by the Paraná and Uruguay rivers that provide 97% of the water discharge contributing with a mean annual flow of 16,000 and 4,000 m³/s, respectively. The Rio de la Plata comprises three well-defined areas: the internal zone that starts at the end of the Parana Delta and is characterized by only freshwater, an intermediate or mixing zone, and an external or marine zone. Distribution and abundance of organisms are strongly associated with environmental factors, but mainly salinity gradients. Water and sediment contamination are the main threats affecting the ecological integrity; and conservation strategies should encompass transboundary policies and agreements oriented to balance socio-economic benefits and ecological requirements at a basin scale.