| Malwathu Oya | |
| Name Other: | Aruvi Aru |
| Pushpin Map: | Sri Lanka |
| Subdivision Type1: | Country |
| Subdivision Name1: | Sri Lanka |
| Length: | 164km (102miles) |
| Source1: | Inamaluwa Mountains |
| Source1 Location: | Matale and Anuradhapura Districts |
| Mouth: | Palk Strait |
| Mouth Location: | Mannar, Northern Province |
The Malwathu Oya (Sinhala; Sinhalese: මල්වතු ඔය Malwathu Oya, Tamil: அருவி ஆறு Aruvi Aru) is the second longest river in Sri Lanka. The river originates in the North Central Province of Sri Lanka and enters the sea on the northwest coast, into the Gulf of Mannar, near Vankalai.[1] It is a seasonal river that spans over through paddy and forest lands, which are used by the inhabitants to cultivate for their survival.[2] [3]
The river basin covers an area of 3284km2 (with a length of 125km (78miles), a maximum width of 40km (30miles) at an average height of 85.5m (280.5feet) above sea level). The average annual rainfall in the basin area is 1223mm. The Ritigala mountain range, which comprises four main peaks (the highest of which is over 900m (3,000feet) high), in the upper reaches of the river, serves as the main catchment.