Ganga is so sacred a name for India that it is incomplete without it. Only sacred river Ganga Completes India.
Once upon a time Paap (sin), challenged Narad Muni the ace-devotee of Lord Vishnu, that he will vanish religion from the face of Universe, Narad accepted the challenge.
Sati, wife of Lord Siva could not tolerate insult of her husband at the Yagna performed by her father Daksha and the Sacrificed herself in the fire. This was an apt opportunity for Taraksasu the demon devil companion of Paap. He conquered the Swarga and terrorised its inhabitants the Devas (Gods). Devas knew that only the son of Lord Siva can kill Tarakasur so by the help of Narad they started their attempts to please Lord Shiva.
Sati took birth again in the form of Uma, as the daughter of king Himachal. Ganga also took birth there as Uma's sister. By Narad's active help Shiva pleased on Uma's meditation and married her. Ganga was taken away to Swarga by Lord Brahma for a sacred mission.
In the meantime a son of Shiva was born to Uma named Kartikeya Tarakasur taking him to be his future killer abducted him and tried to kill him but again by the help of Narad Kartikeya was saved and taken to Swarga when he was brought up under the kind guidance of Ganga.
Maharaja Sagar, King of Ayodya was performing his hundredth Ashvamedh Yagna, but Indra King of Swarga, out of jealousy stole the sacred horse (Ashwa) of the Yagna and hid it at the Ashram of Kapil Muni Sagar's Sons came to Kapil Muni and accused him for stealing the sacred horse. This blame annoyed Kapil and all the Sixty Thousand Sons of King Sagar were burnt to ashes by the anger of the Kapil Muni. Learning this King Sagar also died of shock and his only remaining son Anshumanthen decided by the suggestion of Narad Muni to bring Ganga on to the Earth so that his dead brothers could be enliven and get ultimate peace and the civil of Paap also could be disappeared from the Earth.
But Anshuman's and his Son Dileep's continuous prayers and meditation to bring Ganga on the Earth remained unfruitful - they could not please Ganga. Ultimately Dileep's King Bhagirath resolved with undaunted faith and prayed Ganga from heart of his hearts and as the result Ganga pleased on him and prepared herself to come the Earth but.
She would come to the Earth with terrible force and will straight away go to Patal Lok piercing the Earth if it is not stopped on Earth by a power greater than all other powers-who this power could be?
For the answer you will have to witness the ultimate event with your eyes-of course by seeing HAR HAR GANGE.
(From the official press booklet)