Riacho Porteño is a riacho — a small river or stream channel — located in Formosa Province in the Gran Chaco region of northwestern Argentina, situated at approximately 25°11′47″ S, 58°05′57″ W. This waterway flows through the lowland subtropical wetlands characteristic of the Formosa region, an area defined by flat terrain, dense riparian vegetation, and a network of interconnected water bodies including lagunas, esteros, and riachos that collectively form one of South America's most biologically diverse freshwater ecosystems. The surrounding landscape is part of the broader Pilcomayo basin, a region renowned among South American anglers for its exceptional diversity of native fish species. The warm, productive waters of Riacho Porteño support a rich assemblage of fish, making it a compelling destination for anglers interested in exploring the wild, largely undeveloped fishing waters of the Argentine Chaco.