Here's what I found on Wiki:

 

Another name that Ganga is known by is Jahnavi. Story has it that once Ganga came down to earth, on her way to Bhagiratha, her rushing waters created turbulence and destroyed the fields and the sadhana of a sage called Jahnu. He was angered by this and drank up all of Ganga's waters. Upon this, the Gods prayed to Jahnu to release Ganga so that she could proceed on her mission. Pleased with their prayers, Jahnu released Ganga (her waters) from his ears. Hence the name "Jahnavi" (daughter of Jahnu) for Ganga.

 

Ok, so who is jahnavi? http://srikantha.wordpress.com/2008/07/31/hello-world-youve-got-news/

:)