PILCOMAYO RIVER

Spanish Ro Pilcomayo, chief western tributary of the Paraguay River, south central South America. It rises in the eastern Andes Mountains, in Bolivia, and flows in a southeasterly direction through the Gran Chaco plains of Paraguay to join the Paraguay River opposite Asuncin, after a course of 1,550 mi (2,500 km). Its lower course (about 410 mi), used for navigation by small craft, flows through a number of small channels separated by bars and shifts direction with each flood season. The Pilcomayo (Guaran: River of the Birds) forms part of the international border (delimited in 1945) between Formosa Province (Argentina) and Paraguay.