The Thamirabarani or Tamraparni or Porunai is a perennial river that originates from the Agastyarkoodam peak of Pothigai hills of the Western Ghats, above Papanasam in the Ambasamudram taluk.

[2] It flows through Tirunelveli and Thoothukudi districts of the Tamil Nadu state of southern India into the Gulf of Mannar.

[9] Other name derivations include the Pali term "Tambapanni", "Tamradvipa" of Sanskrit speakers and "Taprobana" of ancient Greek cartographers.

[14] The movement of people, including the faithful, trade merchants and toddy tapers from Tamraparni river to northwestern Sri Lanka led to the shared appellation of the name for the closely connected region.

[15] A Miami-based Beta Analytic Testing Laboratory published a report on 2021 which claimed that the Tamirabharani civilization along the banks of the river dates back to 3,200 years.

[16] The Thamirabarani River originates from the peak of the Pothigai hills on the eastern slopes of the Western Ghats at an elevation of 1,725 metres (5,659 ft) above sea-level.

The Pachaiyar River which originates from the Kalakkadu reserve forests at about 1,300 metres (4,300 ft) above sea level joins the Thamirabarani near Tharuvai village in Palayamkottai Taluk.

[citation needed] The river drains into Gulf of Mannar near Punnaikayal in Tiruchendur taluk of Tuticorin district.

It flooded again in 2015 with water entering the Kurukuthurai Murugan Temple, In December 18,19 2023 due to Massive rain fall in River Catchment area this river flooded again it discharged Maximum n 4.5 lakh Cubic feet water on Bay of Bengal .

The Gadananathi River has 6 anicuts and a reservoir of 9,970,000 cubic metres (8,080 acre⋅ft), and irrigates 38.87 square kilometres (15.01 sq mi) of wetlands.

The Ramanadhi has 7 anicuts, a reservoir of 4,300,000 cubic metres (3,500 acre⋅ft), and irrigates 20.23 square kilometres (7.81 sq mi) of wetlands.

Pachaiyar River has 12 anicuts and irrigates 61.51 square kilometres (23.75 sq mi) of wet and dry lands.

Snakehead fishes are locally called as Viraal in Tamil and all the species are consumed as food around the regions of Thamirabarani when they enter paddy fields.

Because of the presence of huge number of native Snakehead fishes, the Alligator Gar invasion is not spreading and under control.

[citation needed] Other fishes belong to genus Puntius, Devario, Etroplus, Mystus, Aplocheilus, Dawkinsia, Garra, Glossogobius, Macrognathus, Batasio, Barilius, Badidae, Clupisoma, Nemacheilus, Oreichthys, Oryzias, Osteobrama, Raiamas, Salmophasia, Tor (Masheer), Xenentodon, are commonly found in this river.