The interesting story of the origin of River Kaveri, which is known as the Ganga of the South, is associated with Sage Agastya and Lord Ganesha. The holiness of the Cauvery River
Legend has it that once all the saints of world assembled in the Himalayas to hear Hindu God Shiva talking about the secret of the Veda and Tantra. When all the pious people were assembled in Himalayas , the earth tilted. To restore the balance of the earth, Shiva asked Sage Agastya to go south as the spiritual strength of Agastya was equal to that of all the saints in the world.
When he went to South crossing the Vindhya mountain range, he also carried with him Ganga water in a pot (Kamandalu). When Sage Agastya placed his pot on ground to meditate in the South, Ganesha in the form a crow came and tipped the pot down. Water flowed out of the pot and it turned into the Kaveri River
In another version of the story, Ganesha came in the form of a rat.
There is also another popular story associated with Origin of Kaveri River – in this legend Lopamudre, an incarnation of Goddess Parvati, who came to assist the Mohini incarnation of Vishnu, later took birth as the daughter of King Kavera. She was later married to Sage Agastya. But before marrying Lopamudre took the word from Agastya that if she was left alone for too long she will become a river and disappear. Soon Agastya had to leave Lopamudre alone and she became the Cauvery River