Paraguay River 98% of the country's inhabitants. As such the river is considered perhaps the key geographical feature of the country with which it shares its name. Some after flowing through the middle of Paraguay, at the confluence with the Pilcomayo River and passing the Paraguayan capital city, Asunción, the river forms the border with Argentina, flowing generally south-southwesterly for another before it reaches its end, joining with the Paraná River. The Paraguay River is the second major river of the Rio de la Plata Basin, after the Paraná River. The Paraguay's drainage basin, about , covers a vast area that includes
Geography of Paraguay Paraná; the mountain chain has an average height of . Separated from the Eastern region by the Paraguay River, the Chaco region is a vast plain with elevations reaching no higher than and averaging . Covering more than 60 percent of Paraguay's total land area, the Chaco plain slopes gently eastward to the Río Paraguay. The Paraguayan Chaco is subdivided into two parts. The "Alto Chaco" (Upper Chaco), also called "Chaco Seco" (Dry Chaco) is the western three-quarters of the region, bordering on Bolivia, while the "Bajo Chaco" (Lower Chaco) or "Chaco Húmedo" (Humid Chaco) borders on the Paraguay River.