The river Arasalar (Tamil: அரசலாறு) is a branch of Cauvery which split into 5 different rivers when it enters into Tanjore District from Trichy. Exactly in the place near to Pullambadi where the River Cauvery been stopped by Lower Anaicut and from Tiruvaiyaru (separation of 5 rivers) this Arasalar separates from River Cauvery.
This Arasalar takes is course from Tiruvaiyaru of Tanjore, covers and travels through Kumbakonam and enters into the Sea of Bay of Bengal at Karaikal, Where Karaikal once served as a River Port till 19th century where the Yachts and "Marakkalam" ships of Karaikal Marakkayar (also called 'Maricars'/'Maraikkayars') harboured in and, loaded and unloaded the Goods and materials towards Exports and Imports. The Dockyard by name "HMTS Pandagasalai" that is situated 2 km from the Sea Shore stands as an evidence for the same to proclaim that Karaikal was once a traditional River Port through the River Arasalar. From this River port Karaikal got connected with Siam ( Now 'Thailand'), south east and far-east Asian countries, Middle East and African Countries in its tradeline
The historical Novel by name "Ponniyin Selvan" that describes the life of Rajaraja Chola, written and scripted by the Tamil writer Shri. Amarar Kalki speaks a lot about Arasalar.