Lagoa dos Patos

Lagoon in Rio Grande do Sul, Brazil

Lagoa dos Patos (laˈɡoɐ dus ˈpatus; English: Ducks' Lagoon) is the largest lagoon in Brazil and the largest coastal lagoon in South America. It is located in the state of Rio Grande do Sul, southern Brazil. It covers an area of ,

Lagoa dos Patos is separated from the Atlantic Ocean by a sandbar about 5 mile (8 km) wide. The Jacuí Guaíba and Camaquã Rivers empty into it, while the navigable São Gonçalo Channel, which enters Lagoa dos Patos near the town of Pelotas, connects Lagoa dos Patos to Lagoa Mirim to the south. The lagoon's largest and most fertile island is the Ilha dos Marinheiros, which is located near the eastern shore. The island is geopolitically part of the municipality of Rio Grande. The lagoon hosts a rich biodiversity, including fresh and brackish water fish, and water birds such as black necked swan, coscoroba swan and Chilean flamingo. and exceptionally southern right whales are found at the Rio Grande outlet.

The lagoon has average length and width of and , respectively. It covers a surface of , slightly smaller than Jamaica, and occupies nearly one third the area of the Coastal Plain of the state of Rio Grande do Sul. The lagoon roughly runs NE SW, with an average depth of almost , and mean tidal amplitude of 0.45 m. At its southern end, near Rio Grande city, the only inlet of Lagoa dos Patos has a mean discharge of Sea water penetrates northwards into the lagoon up to 200 km during exceptional conditions favored by southern winds, low water levels in the lagoon, and spring tides. The lagoon receives freshwater from about , mostly from the catchment basin of the Guaíba River system, whose mouth is located in Porto Alegre the Jacuí Delta at the northwestern end of the lagoon. The coastal plain bordering the lagoon typically has elevations that reach up to 6 m, mostly consisting of sandy deposits interrupted by small inlets. Those spits rise in average 1 m above the mean water level and on the west margin of the lagoon their submerged part extends about 15 km into the water body.