The Cauvery theertha has sacred qualities ever since its origin. It possesses special blessings from Sage Agasthya who has Installed numerous shivalinga on the banks of Cauvery all the way. There are only 3 divya mangala roopa of Sri Hari in the name of Aadi Ranga, Madhya Ranga and Anthya Ranga viz., Sri ranga pattana (Mysore) Sri Ranga (Trichy) and Parimala Ranga (Mayavaram).
This is the reason king among saints and the fore runner of bringing the Bagavata Cult through writing poetries praising Sri Hari, Sri Sri Padarajaru wrote in one of his song Mangala mooruthi sri rangana Sri padangala nodadha Kangalidhyathako ( Means What is the use of eyes which is not doing dharshan of Sri Ranganatha)
The Cauvery Theertha flowing in this holy city Srirangam is considered to be the vanisher of sins of Ganga river which clears all the sins of persons who take this bath in her. Such is the specialty of Cauvery and her name and fame are praised by the 1000 tongued Adhi Shesha. As we all know, reptiles snake has two tongued (1 tongue splitted in to two at its leading end) so this Shesha is parsing Ranganatha for his glory in the other splitted tongue.