Riacho Porteño is a permanent watercourse in Formosa province, Argentina, flowing west to east across more than 300 kilometers through the departments of Patiño, Pilaga, and Pilcomayo. It originates from waters fed by Laguna Salada, which collect at a dike structure near Estanislao del Campo before the channel proper begins. From there it runs roughly parallel to Ruta Nacional N° 86, passing through old paleochannels, interconnected lagoons, and wetlands before joining the lower Río Pilcomayo. The riacho flows over the alluvial fan of the Río Pilcomayo, specifically across the ancient Estero Patiño, and is fed downstream by the Bañado La Estrella below Ruta Provincial N° 28.

Paddling on Riacho Porteño takes place in at least two distinct sections. One stretch runs near the city of Clorinda, where organized canoe trips of two days have been offered, with paddlers putting in near Clorinda and finishing in the city itself. A second area of kayak activity occurs near the locality of Siete Palmas. The western reaches near Estanislao del Campo, around the dike where the riacho originates, have also attracted visiting anglers and paddlers drawn to the relatively undisturbed character of that zone.

The corridor passes through dense gallery forest typical of the Chaco region, and wildlife encountered on the water includes yacarés (caimans), carayá monkeys, coatis, and a wide variety of bird species. The landscape is characterized by thick riparian vegetation and an overall sense of low human impact, particularly in the western sections.

Water quality along the riacho varies with local rainfall, which periodically dilutes the water. INTA researchers have analyzed parameters including conductivity, dissolved solids, carbonates, sulfates, chlorides, and arsenic at multiple sampling points. Conductivity and dissolved mineral content can vary significantly depending on rainfall patterns. Paddlers should be aware that arsenic has been flagged as a parameter of concern in scientific assessment.

Formosa's tourism ministry has identified Riacho Porteño as a resource with tourism development potential, and the locality of Laguna Naineck, situated along the riacho's course, has been noted in connection with hydraulic infrastructure works in the area.