Nandalar River

 Nandalar  (நண்டலாறு) is a branch river of Cauvery River and flowing between Tiruvarur district and Mayiladuthurai district of the Indian state of Tamil Nadu. It act as a border line for Thiruvarur and Mayiladuthurai Districts.

Meaning
Nandalaru => Nandu(Crab)+Kal(Rock)+Aaru Crab's Fossil in Rock found in this river. So this river got the name as Nandalaru.

Origin
 Nandalar  is a branch of River Cauvery.Nandalar river split from Cauvery near Kumbakonam and it flown through Kumbakonam, Komal, Avazhikkarai, Nallaathur. It drained in Bay of Bengal between Chandrapadi and Tharangambadi.