- The Vaigai basin lies entirely in the state of Tamilnadu .
This basin is bounded by
- the Varushanadu hills, the Andipatti hills, the Cardaman hills and the Palani hills on the West
- by the Palk strait and Palk Bay on the East.
Source of the river
- The Vaigai river rises on the Eastern slopes of the Varushanadu hills near Kottaimalai in the Madurai district
- It flows in the Northerly and North-Easterly directions up to its confluence with the Varahanadhi and then takes a turn towards the East and South-East to flow through Madurai, Sivagangai and Ramanathapuram districts.
- The river Vaigai discharges into Ramnad big tank and some other tanks.
- The surplus water from the tanks finally discharges into the Palk Bay near Mandapam.
Vaigai River Tributaries
- On its way, the Vaigai receives two important tributaries namely, the Suruliyar and the Manjalar on its left bank.
- The Suruliyar, the principal tributary of the Vaigai also rises in the Eastern slopes of the Varushanadu hills and flows in the North and North-Easterly direction.
- It receives Theniar on its left bank, just before its confluence with the Vaigai. .
- The Manjalar another major tributary rises in the Palani hills and flows generally in the Easterly direction before joining the Vaigai below the Vaigai dam.
- The Manjalar is joined by the Marudhanadhi on its left bank before joining the Vaigai.
- The Vaigai also receives another minor tributary namely, the Varahanadhi on its left bank below the Vaigai dam.