The Thamirabarani — or Porunai in Tamil literary tradition — flows from the high Western Ghats at Pothigai Hill east across the plain and into the Gulf of Mannar near Punnaikayal. It is the only year-round river in southern Tamil Nadu and the reason Tirunelveli district has been intensively cultivated for at least three millennia.
In the city itself the river is crossed by several bridges; the long view downstream from the Palayamkottai bridge, with women washing clothes on the broad stone steps and the gopurams of the Nellaiappar Temple in the distance, is one of the more characteristic Tirunelveli scenes. Upstream at Cheranmahadevi and Ambasamudram the river runs through palmyra-fringed countryside that is essentially unchanged in look from descriptions written 1,500 years ago.