Onilahy River
| Onilahy River | |
|---|---|
Onilahy River estuary | |
Map of the Onilahy River watershed | |
| Location | |
| Country | Madagascar |
| region | Atsimo-Andrefana, Anosy |
| Cities | Mandrofify, Ambolofoty |
| Physical characteristics | |
| Source | |
| • location | near Betroka |
| Mouth | Bay of Saint-Augustin |
• location | Saint Augustin, Mozambique Channel |
• elevation | 0m |
| Length | 525 km (326 mi) |
| Basin size | 31,600 km2 (12,200 mi2) |
| Discharge | |
| • location | Near mouth |
| • average | (Period: 1971–2000)183 m3/s (6,500 cu ft/s) |
| Basin features | |
| Protection status | |
| Official name | Zones humides de l'Onilahy |
| Designated | 22 May 2017 |
| Reference no. | 2304 |
Onilahy is a river in Atsimo-Andrefana and Anosy (Toliara Province), southern Madagascar. It flows down from the hills near Betroka to the Mozambique Channel. It empties at St. Augustin (23°34′00″S 43°45′00″E / 23.5666667°S 43.75°E), and into the Bay of Saint-Augustin.
Two species of cichlids are endemic to the river basin, but Ptychochromis onilahy is probably already extinct and the remaining range of Ptychochromoides betsileanus covers less than 10 square kilometres (3.9 mi2).