- The Thamiraparani or Tamraparni or Poruna is the only perennial (continuous flow of water) river in Tamil Nadu.
- This is the shortest river in the state, the Thamirabarani starts in Pothigai hills of the Western Ghats in the Ambasamudram taluk, flows through Tirunelveli and Thoothukudi districts and empties at Korkai (Tirunelveli district) into the Gulf of Mannar (Bay of Bengal). It thus originates and ends in the same state.
- The river supports wildlife such as the Nilgiri marten, slender loris, lion-tailed macaque, white spotted bush frog, galaxy frog, Sri Lankan Atlas moth and the great hornbill.
- Besides the ecosystem services it provides, the river also has historical value for the people of the state. It is mentioned extensively in Sangam Era literature.
|Koraiyar||Mundanthurai reserve forests||Karaiyar Dam|
|Servalar River||Mundanthurai reserve forests||Papanasam Reservoir|
|Manimuthar River||Manjolai hills||Aladiyoor|
|Gadananathi River||Agasthyamala Biosphere Reserve||Tiruppudaimaruthur|
|Pachaiyar River||Kalakkadu reserve forests||Tharuvai|
|Chittar River||Kutralam Hills||Sivalaperi|
|Ramanathi River||Agasthyamala Biosphere Reserve||Kizha ambur|