Onilahy River

The Onilahy River is Madagascar's second longest river, beginning on a hill near Betroka in Toliara Province in southern Madagascar. It has a length of 326 miles and is home to two endemic cichlid species, Ptychochromis onilahy and Ptychochromoides betsileanus. This is one of the longest rivers in Madagascar. It empties into the bay of Saint-Augustin on Madagascar's south-western coast. Two cichlid species are indigenous to the river basin, however Ptychochromis onilahy is likely extinct, while Ptychochromoides betsileanus' remaining range is fewer than 10 square kilometers (3.9 sq mi).

Near Beadabo are the Onilahy river's sources. It flows from Ankilimary to Benenitra, Ehara, Bezaha, and Antanimena via Benenitra, Ehara, Bezaha, and Antanimena. Near Tameantsoa, it is bridged by the RN 10. The mouth of the Onilahy river is 35 kilometers south of Toliara (Tuléar) in the Indian Ocean in Saint Augustin, Madagascar.

Sakamena river, Evasy, Ianapera river, Isoanala river, and Ihazofotsy are its primary affluents from the south. Sakondry, Taheza, Sakamare, and the Imatoto river are all to the north.

Length: 525 km (326 mi)