A major water source to the Nanguneri taluk, Nambiyar River originates from the western slopes of the Western Ghats, at an altitude of 1500 m above sea level. The river has a total length of 45 km and its entire course has been restricted to the Nanguneri taluk itself. Parattaiyar and the Thamaraiyar are its main tributaries. These tributaries join Nambiyar at the foot of the Mahendragiri hills. It eventually merges with the
Gulf of Mannar
at Tiruvambalapuram village.