The São Gonçalo Channel () is a navigable channel connecting two large coastal lagoons,

Lagoa Mirim Lagoon Mirim (Portuguese, ) or Merín (Spanish, ) is a large estuarine lagoon which extends from southern Rio Grande do Sul state in Brazil into eastern Uruguay. Lagoa Mirim is separated from the Atlantic Ocean by a sandy, partially barren isthm ...

and

Lagoa dos Patos Lagoa (Portuguese for ''lagoon'') may refer to the following: People * Barbara Lagoa, Cuban-American federal judge Places Brazil * Campina da Lagoa, Paraná * Lagoa, Paraíba, Paraíba * Lagoa, Rio de Janeiro, a quarter of Rio de Janeiro * Lagoa ...

, in the state of

Rio Grande do Sul Rio Grande do Sul (, ; ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative units of Brazil#List, fifth-most populous state and the List of Brazilian s ...

in southern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. At its eastern end, it separates the municipalities of

Rio Grande The Rio Grande ( or ) in the United States or the Río Bravo (del Norte) in Mexico (), also known as Tó Ba'áadi in Navajo language, Navajo, is one of the principal rivers (along with the Colorado River) in the Southwestern United States a ...

to the south from

Pelotas Pelotas () is a Brazilian city and Municipalities of Brazil, municipality (''município''), the fourth Largest cities in Rio Grande do Sul by population, most populous in the southern state of Rio Grande do Sul, after Porto Alegre, Caxias do Su ...

to the north.

Course

The Mirim-São Gonçalo basin covers an area of about , of which 47% are in

and 53% in

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

. Its main source of water, the

, is located in the coastal plain, with an average width of 20 km and an area of , of which 2,750 km² are in Brazilian territory and 1,000 km² in Uruguayan territory. The two systems are connected by a natural channel called São Gonçalo, which drains from Lagoa Mirim to

. However, in times of drought, this flow is reversed and the salt water flows from Lagoa dos Patos through the São Gonçalo canal to Lagoa Mirim. The São Gonçalo Channel is located in the west-southern part of the Lagoa dos Patos system. The natural flow regime of the canal is complex, with periodic reversals in the direction of flow, which is why the canal is called the Gonçalo Canal. The average discharge is to and the flow velocity is 0.6 m/s. The maximum freshwater discharge reaches during floods, while the discharge is zero during long dry seasons, when the flow is generally directed towards the

. This natural channel has a sinuous course, varying in width from to and in depth up to . The region is part of the geomorphological provinces of the

Coastal Plain A coastal plain (also coastal plains, coastal lowland, coastal lowlands) is an area of flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and an upland area. Formation Coastal plains can f ...

and the Uruguayo-South-Rio-Grande Shield, and in the Brazilian part of the region are Aceguá,

Arroio do Padre Arroio do Padre (, Portuguese language, Portuguese meaning Priest's Stream) is a Brazilian Municipalities of Brazil, municipality in the southeastern part of the state of Rio Grande do Sul. Its 2020 population was 2,951. Much of the population ...

Arroio Grande Arroio Grande ( Portuguese meaning the big stream) is a Brazilian municipality in the southern part of the state of Rio Grande do Sul. The population is 18,238 (2020 est.) in an area of 2513.60 km². Its second industry is agriculture which ...

Bagé Bagé () is a Brazilian municipality located in the state of Rio Grande do Sul. In 2020, its population was 121,335 in a total area of 4,096 km2. It is the seventeenth largest city in the state according to the 2011 census. The city was f ...

, Candiota, Canguçu, Capão do Leãu, Pedro Osório,

Pinheiro Machado Pinheiro Machado () is a municipality in the state of Rio Grande do Sul, Brazil. History Pinheiro Machado is one of the oldest towns in the state of Rio Grande do Sul. Until 1830, the area was owned by the city of Rio Grande. After it became ...

, Piratini,

Santa Vitória do Palmar Santa Vitória do Palmar (lit. "Saint Victoria of the Palms") is a Brazilian city and municipality. It is the southernmost municipality in Brazil, located in the state of Rio Grande do Sul. To the west of the municipality is the Lagoa Mirim an ...

and Turuçu.

Ecology

The lake and the wetlands around it form one of the main hydrographic basins of

, which contains a wide variety of flora and fauna and, together with

, forms the largest lagoon complex in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. The

and its surrounding wetland complex form one of the main transboundary river basins in

, which is of great ecological and economic importance. The main uses of the water are irrigation and human consumption. Two important environmental reserves, the

Taim Ecological Station The Taim Ecological Station () is a federally-administered ecological station in the state of Rio Grande do Sul, Brazil. Location The coastal marine ecological station, which has an area of , was established on 21 July 1986. It is administered b ...

in Brazil and the Humedales del Este in Uruguay, are located on the shores of the basin. The Taim Ecological Station is a federal nature conservation unit of integrated protection and aims to protect the environment. Known worldwide as one of the most important nature reserves, it preserves marshes, lakes, fields, dunes and forests, and is home to a wide variety of plant and animal species. The Humedales Del Este eastern wetlands in Uruguay, have been included in the list of the Convention on Wetlands of International Importance -

Ramsar Convention The Ramsar Convention on Wetlands of International Importance Especially as Waterfowl Habitat is an international treaty for the conservation and sustainable use of Ramsar site, Ramsar sites (wetlands). It is also known as the Convention on We ...

, which is made up of an ecosystem of about 560,000 hectares, including 10 protected biosphere reserves, national parks (Bañados de San Miguasn, Laguna de Josrón -

Isla de Lobos The Isla de Lobos is a small island located about southeast of Punta del Este (Uruguay) in the Atlantic Ocean. An islet lies east of the island. Since 2024 it makes up the ''Island and Islet of Lobos and their Submerged Environment National Par ...

, Cerro Largo); Protected landscapes (

Cerro Catedral Cerro Catedral is a mountain located from San Carlos de Bariloche, and inside the Nahuel Huapí National Park, in Patagonia, Argentina. The complex is one of the most important ski resorts in South America and the Southern Hemisphere, with a ...

- Sierra de Sosa, Asperezas de Polanco, Sierra Del Tigre,

Quebrada de los Cuervos The Quebrada de los Cuervos (Spanish language, Spanish for ''Crows Ravine'') is an important landform in Treinta y Tres Department, Uruguay. Crossed by the Yerbal Chico creek, it constitutes a natural protected area. This Important Bird Area (IBA) ...

); Protected areas with managed resources ( Laguna Merín and India Muerta).

Sluice system

The lock separates the São Gonçalo Canal from the

at 15 km and the

at 61 km. The sluice dam was built in 1977 to prevent the inflow of salt water into the Lagoa Mirim, as a result of the development of the two countries between

and

. This navigation channel has two leveling sluice gates 17 m high and 8 m wide. The system of operation of the sluice depends on the fluviometric level of the Lagoa Mirim: when the average level of the Lagoa Mirim is close to 1 m below sea level, the sluice starts to regulate the flow between the São Gonçalo channel and the Lagoa dos Patos. The water level in the Lagoa Mirim is controlled during this period by partial or complete closure of the lock gates and by reducing the opening time of the navigation lock. During the remaining time the locks will remain partially open. In summer, the lock channel is opened four times a day at fixed times to allow the passage of vessels.

Tributaries

Major tributaries of the Mirim-São Gonçalo basin:

References

{{DEFAULTSORT:Sao Goncalo Channel Bodies of water of Brazil Channels Landforms of Rio Grande do Sul