PILCOMAYO RIVER: ROUTE, MOUTH, TRIBUTARIES, FLORA - GEOGRAPHY - 2025

The Pilcomayo River is a tributary of South America that runs through Bolivia, Paraguay and Argentina. It is part of the La Plata basin and extends over a territory of approximately 290,000 km².

It is born in the Bolivian mountain range and is constituted as a tributary of the Paraguay River, to which it contributes its waters at its mouth. Due to the variety of the reliefs that it crosses in its 1,000 km of route in a northwest-southeast direction, it is a watercourse with a very varied behavior, with the presence of falls, rapids and flood plains.

The Pilcomayo has a period of flood marked by the rainy season. Photo: Pertile

History

Training

Its history begins in the Pleistocene, a time in which it participated in the formation of the Great American Chaco, depositing its waters in a large lake that has now disappeared that gave way to the current overflow plains, with its swamps and estuaries.

First records

The first record of its journey was made in 1721 by the Paraguayan Jesuit Gabriel Patiño, who was part of the commission ordered by the civil government of the province of Tucumán. Father Patiño's company was made up of Spanish religious and seventy evangelized Guarani. Their official mission was to find a path that would connect the settlements of Paraná and Chiquitos, while the Jesuits looked for new indigenous ethnic groups to evangelize.

Although this mission was unsuccessful, Father Patiño managed to draw a map of the region, with which they determined that the Pilcomayo and the Bermejo rivers constituted different currents. Thus they discovered the Estero de Patiño, which occupied 1,500 km ² of flooded land with an approximate length of 100 km.

Other expeditions

A new expedition was undertaken in 1741 by Father Castañares, another Jesuit who took charge of the company with the aim of finishing Father Patiño's unfinished mission. His mission had a tragic end, in 1742 he died along with the rest of his companions at the hands of the Tobas, an ethnic group that lived in the Central Chaco.

Many attempts were undertaken by the governments of the region seeking to map a free passage linking the territories by the river. In 1882 the Bolivian government commissioned the French explorer Jules Crevaux with a trip that departed from San Francisco de Pilcomayo, seeking an exit to the Atlantic. This expedition suffered the same fate as that of Father Castañares and its members died at the hands of the Tobas under circumstances that were not clarified.

The following year, the Bolivian government organized another expedition commanded by Dr. Daniel Campos, who took up the steps of the French explorer followed by a large armed contingent. In a place between Teyú and Caballo Repotí -current Weenhayek territory- they founded the Crevaux Colony.

The Argentine government organized an exploration of the Pilcomayo River with ships of different depths, specially prepared to overcome the obstacles that were already well known to date. In command of the squadron they placed the frigate captain Juan Page, who left Buenos Aires in January 1890. On May 12 they had reached the Pilcomayo River and began their exploration with two ships: the Bolivia and the General Paz.

On his way upriver, narrow and shallow passes made Captain Page make the decision to abandon General Paz. With many setbacks and using ingenuity to build dams to float his boat, Page continued to advance until July 20, when he was forced to return sick, downriver in a canoe. He died before he could reach a port on August 2, 1890.

Many other explorers found their deaths in the fearsome river and concluded that the Pilcomayo was not navigable at any time of the year, because its floods and its channel were not regular.

The affairs around the riverbed are not limited to its exploration. The establishment of the binational borders marked on its channel had to be reviewed and highlighted by the variability that it presents between the wet and dry periods, in which many times it has completely disappeared.

In 1933, the Pilcomayo River abandoned its traditional channel between Argentina and Paraguay when it entered Argentine territory. At that time, a drying process was evident that affected the Patiño estuary and culminated in 1980.

Appearance of Bañado La Estrella

Around 1964, a wetland began to emerge on the Argentine side: Bañado La Estrella. Paradoxically, its formation occurred in parallel to the disappearance of the Patiño estuary, for which the specialists affirmed that it was a normal behavior of the river.

This change generated a conflict between Argentina and Uruguay, centered on the need for water by the existing populations in Uruguayan territory. The event produced constructions on both sides that sought to capture the water from the Pilcomayo for its use.

In 1989, the governments of Argentina and Uruguay reached an agreement and designed the “Pant Project”, which led to the construction of two canals, one on each side and at the same level, to bring water to both territories.

General characteristics

The Pilcomayo River has characteristics that make it unique. It has been the subject of intense scientific research to understand its behavior, as well as its place and importance within the La Plata basin.

International river

The Pilcomayo river basin is shared by three countries, which is why it is considered an international river. It was born in Bolivia, in the Andes Mountains from where it descends to serve as the border between that country and Argentina. In the plain of the Great American Chaco it draws some sections of the border between Paraguay and Argentina.

Growing

The Pilcomayo has a period of flood that is marked by the rainy season at its head, between December and January.

Its flood begins in February and reaches its maximum levels in April. It presents the minimum records in late winter and early spring. Its months of descent are between May and December.

Its flow varies considerably between periods of flood and dry season and depends largely on the place where it is measured. In Bolivian territory, the flow is much more impetuous, reaching maximum records of 6,500 m ³ / s in the humid period; while in the Central Chaco it can disappear during the dry period.

Bathed and estuaries

As it passes through the Andes Mountains, the waters of the Pilcomayo River drag a large amount of sediment that it carries in suspension, to deposit them on the plains of the Great American Chaco, forming with its accumulation and overflowing of its waters, baths and estuaries.

The Pilcomayo River is considered one of the rivers that carries the most sediment in suspension in its waters, with an impressive average rate of 125 million tons per year.

This is due to the fact that the terrain on which it moves is made up mainly of clay, sand and gravel, materials that are highly erodible by the direct action of the river bed and indirectly by the rains that run into it.

Until 1980, the Patiño estuary existed in the Paraguayan department of Presidente Hayes, near the border with Argentina, which due to a drying process stopped receiving food from the Pilcomayo and dried up.

In parallel, as of 1964, the Bañado La Estrella began to form in the Argentine province of Formosa, a region very close to the extinct Patiño estuary, which is why specialists affirm that both events are connected by a change in the river channel. Pilcomayo.

The Bañado La Estrella is considered the second largest wetland in Argentina, with a length that varies between 200 and 300 km and a width of between 10 and 20 km.

At its exit from the Andes Mountains, at its entrance to the Gran Chaco Americano plain, at the height of the city of Villa Montes in the Bolivian province of Tarija, the Pilcomayo forms a pluvial fan that extends to its mouth at the Asuncion, Paraguay.

It has an approximate magnitude of 700 km in length and 650 km in width, the latter is modified considerably between the rainy and dry periods with historical records of setbacks of up to 100 km.

Extinction of the Pilcomayo channel

The sedimentation of the large amount of solid waste, a product of the pollution that the Pilcomayo carries in suspension through its channel, generates a unique phenomenon in the world: the extinction of the channel or silting.

In addition to poor river conservation policies, the lack of rainfall in Bolivia has progressively caused the Pilcomayo to dry up completely.

Currently it is an ecological problem that has set off the alarms of the countries it crosses, which have initiated different plans to manage actions in favor of its maintenance and for the rescue of the animals that make life in its ecosystem, which have been seriously affected. by sedimentation.

Birth, route and mouth

The Pilcomayo River is born at an approximate height of 5,000 meters above sea level in the Cordillera de los Frailes, in the Bolivian Andes, specifically in Cerro Michaga, which is located west of the department of Potosí.

Then it runs in a southeasterly direction to its mouth in the Paraguay River. In Bolivian territory it touches the departments of Potosí, Chuquisaca and Tarija, where it leaves its mountainous section and enters the plain of the Great American Chaco.

In the Chaco it forms marshlands and estuaries that touch small towns such as Santa Victoria and Misión de La Merced, near the Hito Esmeralda that marks the border between Bolivia, Argentina and Paraguay.

It continues its way south between Argentina and Paraguay, passing near the cities of Clorinda and La Asunción in the departments of Formosa and Presidente Hayes respectively. It reaches the Paraguay River near Asunción.

Main cities that travels

On the Pilcomayo river basin there have been settlements of 20 indigenous ethnic groups distributed among the three countries. Some of them are the Tapietes, the Tobas, the Guaraníes, the Wichis and the Weenhayek.

Due to the wandering behavior of its riverbed, there are no cities placed directly on its banks. However, it passes near some important ones like Potosí and Villa Montes in Bolivia; Formosa and Clorinda in Argentine territory; Villa Hayes and the Asunción in Paraguay.

Tributaries

Among the tributaries of the Pilcomayo are the Camatindi, Tarapaya, Suaruro, Yolanda, Cotagaita, Yamparez, Grande, San Antonio, Chuquiago, Chaco Bañado, Puca Mayu, Huacaya, Caigua and El Puente rivers.

Flora

The Pilcomayo river basin presents a great variation in height that ranges from 5,000 meters above sea level at its source on the Andes Mountains, to approximately 50 meters above sea level at its mouth in the Paraguay River.

It has temperatures from below zero to an overwhelming 47 ° C in the Central Chaco, so its vegetation is very diverse. In the area you can find the Cumandá language, lapacho, black algarrobo, santo, duraznillo, palo bobo, white quebracho, orange payaguá, palo lance, quebracho coronillo, labón, sacha watermelon, samuhú, palo piedra, indigenous salt, espartillo, mistol, cardón, palo negro, pindó, jacaranda and white carob.

Fauna

The animal species present in the Pilcomayo River are also very varied and have adapted to the specific conditions that each climatic type presents.

Mammals include jaguar, tapir, puma, corzuela, capybara, river wolf, South American raccoon, collared peccary, tatabro, tagua and the anteater.

Many birds inhabit humid areas. Among the most common species are crested, bragado, bluish-headed maracana, stork, goose duck, brown hut, parrot, rhea, woodpecker, jabirú, giant nuthatch, flamingo, talking parrot and black bandurria.

It is also inhabited by the white heron, red-billed woodpecker, chajá, cattle egret, chinchero nuthatch, bicolor suirirí, cardinal, blue heron, crested duck, creole duck, red-billed cardenilla, black heron, ventriblanco curutié, tufted hornero and cantil.

Reptiles in the area are alligator, yellow anaconda, Wagler's snake, yarará, green parrot snake, ameiva and tejupyta

Among the fish are diver, mojarra, kelp, toothy Paraguayan, trompudo catfish, tritolo, boga, pequira, water mother, river sole, breast, toad catfish, armed, silverside, painted surubí, chanchita, pacú, black moray eel, piranha, tilefish and tarpon.

References

1. Basin of the Pilcomayo River in Argentina, Argentine Government Interior Ministry (2005), taken from mininterior.gov.ar.
2. History and bravery of the Pilcomayo, Digital version of the Argentine newspaper El Tribuno de Salta, April 15, 2018, taken from eltribuno.com.
3. The problem of the Pilcomayo Basin, website of the Intergovernmental Coordinating Committee of the Countries of the Plata Basin, taken from cicplata.org.
4. Villalba, L, The nature and wealth of the Pilcomayo River, Trinational Chaco Initiative - Moisés Bertoni Foundation, Asunción (Paraguay, 2015).
5. Basin characteristics, Trinational Commission for the Development of the Pilcomayo River Basin, taken from pilcomayo.net.