The Pampas wetlands are the lagoons, marshes and floodable grasslands of the Salado Depression in Buenos Aires Province, Argentina, a near-flat basin of about 170,000 km² (more than half the province) drained by the 640 km Río Salado into Samborombón Bay on the Río de la Plata estuary. Rather than one swamp, they are a chain of shallow lagoons, seasonal bañados and coastal salt marsh set inside farmed grassland, where water lies on the surface because the land barely slopes toward the sea. The coastal end is a Ramsar Wetland of International Importance (site no. 885), Campos del Tuyú National Park has protected its southern shore since 13 May 2009, and the Mar Chiquita coastal lagoon farther south is a UNESCO biosphere reserve. The clearest way to understand them is to follow the Salado from its source to the sea.
El Chañar Lake to Junín: Where the Salado Begins
The river begins at El Chañar Lake near Teodelina, on the boundary between Santa Fe and Buenos Aires provinces, only 40 metres above sea level. That figure explains almost everything downstream. With 640 km to run and 40 m to lose, the Salado drops on average about six centimetres per kilometre, so in wet years water spreads sideways faster than it moves forward. The Pampas as a whole cover more than 1,200,000 km² across Argentina, Uruguay and southern Brazil, but this belt of Buenos Aires Province has almost no slope, which is why it is called the Pampa Deprimida, the depressed Pampa.
The first city on the river is Junín, 260 km west of Buenos Aires, with 85,420 people at the 2010 census. Junín began as a frontier fort: in the 19th century, before the Conquest of the Desert, the Salado marked the boundary between colonial settlement and land still held by Indigenous peoples, and a citadel was founded on the river on 27 December 1827. The town’s lagoons now earn it a living. A fishermen’s pier and club opened on Lake El Carpincho in 1942, and Lake Gómez drew around 350,000 visitors in the 2006–07 summer season alone, a reminder that in the Pampa Deprimida a lagoon is a local economy as much as a habitat.
Bragado to General Belgrano: Where the Río Quinto Joins the Flood
Below Junín the Salado receives water from far outside the province. The Río Quinto, which rises in San Luis and crosses southern Córdoba, reaches the Salado on the surface near Bragado in wet periods and seeps in underground in dry ones. When it runs high, the basin overflows, and wide areas of cattle land and cropland turn into temporary lagoons and marshes. Much of the Pampa Deprimida is therefore used for cattle breeding rather than crops, because farmers cannot count on a field staying dry.
The Salado then passes Alberti, Roque Pérez, Norberto de la Riestra and General Belgrano, threading between wetlands and lagoons. From the south it collects the Saladillo, the continuation of the long Arroyo Vallimanca, and the Arroyo Las Flores, which meet in the Las Flores Grande and Las Flores Chica lagoons, an extensive wetland on the main channel fed by streams from the Ventania and Tandilia hills. Annual rainfall in the basin averages roughly 800 to 1,300 mm, and storms can deliver 50 mm in an hour, so the river alternates between flood and drought rather than running steadily.
Engineering has tried to speed the water along. Early this century the Arturo Jauretche canal, part of the Plan Maestro Integral for the Salado basin, restored much of the surface link between the Río Quinto and the Salado, and the plan dredged 49 km of the lower river between Canal 15 and Laguna Las Barrancas in Castelli and Lezama, removing about 19 million cubic metres of riverbed. Channelisation of the lower course has improved drainage to a mean flow of about 88 m³/s for a basin where nearly one million people live. Critics point out the cost: the straight canals, most of which discharge in parallel into Samborombón Bay, carry fertile soil and the season’s fresh water quickly out to sea.
Las Encadenadas de Chascomús: A Chain of Lagoons Beside Route 2
Near its lower course the Salado receives one of the best-studied lake systems in Argentina. Las Encadenadas de Chascomús, the “chained” lagoons, are a string of shallow basins linked by streams, draining a catchment of about 80,100 hectares in the partidos of Chascomús and Lezama. The chain starts at Laguna Vitel, between 1,305 and 1,465 ha with a mean depth of only 117 cm. The Arroyo Vitel carries its water into Laguna de Chascomús, which also receives the Valdés, Los Toldos, San Felipe, Tamberas and Brown streams.
Laguna de Chascomús covered 3,013 ha before infilling in the 1970s and 1980s reduced it by about 5 percent. Its surface sits at about 6.5 metres above sea level; above 8 metres it spills over the surrounding fields and sometimes into the town of Chascomús itself, while in 1910 it dried out completely. The town on its eastern shore was founded as a fort on 30 May 1779 and had 30,670 inhabitants in 2001, 123 km south of the capital. Bulrush beds fringe the shallows and support coots and black-necked swans, and the lagoon’s fishery is built on the pejerrey, a silverside prized by anglers; limited commercial fishing has been allowed since 1976.
From Chascomús the 3.6 km Arroyo Girado runs into Laguna Adela, about 2,090 ha, 10.35 km long and no deeper than 2.05 metres. Adela is joined to Laguna del Burro, separated from it only by Provincial Route 2 and the General Roca railway, and drains south through the Arroyo Manantiales into Laguna Chis-Chis, where the chain crosses into Lezama. Because the outlet lies close to the Salado’s mouth, floods on the Paraná or Uruguay push the estuary’s brackish water back toward the sea and let freshwater fish swim up into the lagoons.
Samborombón Bay: 135 Kilometres of Salt Marsh at the Salado’s Mouth
The Salado reaches the coast near Cerro de la Gloria, roughly 170 km southeast of Buenos Aires, in the middle of Samborombón Bay. The bay is a shallow, nearly semicircular sweep about 135 km wide from Punta Piedras in the north to Punta Rasa in the south. Members of Magellan’s expedition are thought to have named it in 1520 after the legendary island of San Borondón, Saint Brendan’s Island. Besides the Salado it receives the 100 km Río Samborombón, the Ría de Ajó and a series of numbered drainage canals cut to empty the flood-prone east of the province.
Its shore is hard to read from the water: low marsh, shell ridges and mudflats so riddled with crab burrows that local people call them cangrejales, and swimming is discouraged. That instability is what makes it valuable. The bay holds an unusually high density of shorebirds, including the buff-breasted sandpiper, and serves as a nursery for fish of the Río de la Plata estuary. It is listed under the Ramsar Convention as site no. 885 and as a Western Hemisphere Shorebird Reserve Network site. On land, the provincial Bahía Samborombón reserve protects a strictly controlled core of 9,311 ha, Rincón de Ajó another 2,311 ha, and the northern coast falls within the Parque Costero del Sur.
Campos del Tuyú and Punta Rasa: One of the Last Pampas Deer Refuges
At the southern end of the bay, in the partido of General Lavalle, Campos del Tuyú National Park covers 3,040 ha between the Río de la Plata, the Ría de Ajó and the Arroyo Las Tijeras. It began as a private reserve run by Fundación Vida Silvestre Argentina and became a national park on 13 May 2009. Its main purpose is to protect one of the last populations of the Pampas deer in Argentina. The species numbers roughly 80,000 animals across South America, mostly in Brazil, and the subspecies of Buenos Aires Province survives in only a handful of places. Geoffroy’s cat, capybara, greater rhea and more than a hundred bird species share the park.
The park has no paved access; its entrance lies about 6 km off Provincial Route 11, and San Clemente del Tuyú is 9 km beyond its eastern edge. At Punta Rasa, the tip of Cape San Antonio, a biological station run jointly by the Argentine Navy’s hydrographic service and Vida Silvestre monitors the migrant shorebirds that use the bay, while the waters off Punta Rasa and General Lavalle draw anglers after black drum.
Mar Chiquita: A Detour South to a Lagoon Open to the Sea
The Salado’s journey ends at Samborombón, but the Pampas wetlands continue down the Atlantic coast. About 30 km north of Mar del Plata lies Mar Chiquita, a long coastal lagoon separated from the ocean by a line of high dunes and open to it through a narrow inlet. Freshwater arrives from the Vivoratá and Dulce streams, which rise in the Tandilia hills, and seawater enters with the tide, giving the lagoon a mixed salinity found in no other lagoon of its kind in Argentina. UNESCO listed the area as a biosphere reserve in the mid-1990s, and in 1998 the national government declared a wildlife refuge of 560.3 km² around it. A walk of just 10 km inland from the beach crosses dunes, salt marsh, brackish and freshwater marsh, Pampas grassland and tala woodland. The resort village on its southern shore had 700 residents at the 2022 census; between 1968 and 1972 the site was also used to launch sounding rockets.
Off the Main Channel: Epecuén and the 1985 Flood
The western edge of the province shows what happens when Pampas lagoons rise with nowhere to drain. Villa Epecuén, a spa village on the eastern shore of Laguna Epecuén about 7 km north of Carhué, was developed in the early 1920s and at its peak could host at least 5,000 visitors. On 6 November 1985 a seiche caused by a rare weather pattern broke a nearby dam and then the dike protecting the village. The water rose to a peak of 10 metres and the village was never rebuilt. It stayed submerged for about 25 years, and its ruins are crusted with salt today. Pablo Novak, who returned in 2009 when the water receded, lived there alone until his death on 22 January 2024.
The two ends of this journey, drained farmland and drowned spa town, frame the region’s dilemma: the same flat ground that makes the Pampas such productive land also makes its water hard to manage. For the drier, farmed side of the story, see this guide to the Pampas plains and the wider overview of Argentina’s geography, or compare the Salado’s lagoons with South America’s largest floodplain in the Pantanal wetlands of Brazil, Bolivia and Paraguay.