The Río Pilcomayo National Park (Spanish: Parque Nacional Río Pilcomayo) is a protected area in the northeastern part of the Argentine province of Formosa, near the border with Paraguay. It was created on September 29, 1951, to preserve natural features such as grasslands, marshes, creeks, lakes, and forests found in the Humid Chaco ecoregion. The park is listed in the Ramsar Convention as a wetland of international importance.
Topography
The park covers a large flat area that was created when a low spot in ancient rocks was filled with materials from living and non-living sources, forming a basin with layers of sediment. The top layers of sediment were shaped by rivers and wind. In the eastern part of the park, fine particles like silt and clay create soils that do not allow water to pass through easily, while the western part has soils with larger particles that let water flow through more easily.
Faults formed when the Andes mountains were created run alongside the Paraguay River. Although the park’s land slopes gently from west to east, there is not much difference in height. These small height differences become important during heavy rains and floods, when water pools form in the lowest areas and are connected by channels.
Hydrography
The Pilcomayo River, after which the park is named, is the main river in the area. During the wet season, the river and its smaller rivers flood nearby lands, forming large areas of connected lakes and wetlands, most of which are temporary. The southern part of the park includes a larger lake named Laguna Blanca, which serves as a home for many types of water birds and as a resting place for migratory birds traveling from the Northern Hemisphere.
Climate
The park is located in a subtropical area with an average temperature of 23 °C (73 °F) each year and an average rainfall of 1,200 millimetres (47 in) annually. Summer temperatures can go above 40 °C (104 °F), but frost sometimes occurs during winter. Winter months are dry, and rainfall is highest in March and November. The area often experiences tornadoes.
Flora
The park can be divided into four separate areas to help classify its plant life. One area is a savanna, which has many Caranday wax palms. This plant is an unofficial symbol of the region and grows tall above a thick layer of herbaceous plants, especially those from the Scirpus genus. Other trees in this area include Acacia caven and Prosopis nigra.
The wetlands are covered with water plants. Floating plants in this area include water hyacinths, Limnocharitaceae, Nymphoides, and Ludwigia.
A third area is near the Pilcomayo River and its old river paths, which often flood. This region is home to riparian vegetation. Trees like figs and sweetwood grow there, along with many types of lianas, vines, and epiphytes.
The fourth area consists of scattered vegetation on higher ground, forming distinct "mountain islands." These areas are often found with Quebracho trees, including Schinopsis balansae and Aspidosperma quebracho-blanco.
Fauna
Higher areas are home to mammals such as the gray brocket, capybara, peccary, howler monkey, and puma. Birds in these regions include chachalacas and rails. The maned wolf lives in lowland areas, along with birds like the greater rhea and seriemas.
The park is also home to jaguars (Panthera onca palustris), which are in danger of disappearing in Argentina. This National Park, along with El Impenetrable in Chaco, are the last safe areas for jaguars in the Argentine Chaco. Other jaguar populations live in the Yungas of Salta and Jujuy, and in the Misiones jungle.
Aquatic areas are inhabited by storks, herons, roseate spoonbills, and ducks. Two types of caimans live here: the broad-snouted caiman and the yacare caiman. Fish in the area include species from the Hoplosternum genus, which can breathe air and survive during dry periods that often affect shallow water bodies.
Snakes in the region include the yellow anaconda (Eunectes notaeus) and Hydrodynastes gigas, a large water snake.