Ganga River is not just an ordinary river, but is the Vishnu Paadodaka, which means it is the charanaamrit of Bhagavan Vishnu. As per SrimadBhagavatam, during the Vamana Avatara, when Bhagavan Vishnu appeared as the son of Aditi and Kashyapa Maharshi, He grew up as a 5yr old Brahmin boy and underwent Upanayana (Janeu Sanskar), after which the devatas gifted Him various things. Vaamana asked for 3 steps of Bhoomi from Bali Chakravarthy. Bali Chakravarthy granted Him 3 steps of Bhoomi. Vaamana grew into His large Trivikrama form and measured the three worlds with His feet. When His toenail touched the covering of the Brahmanda, that covering itself broke away. Lord Brahma, at that time, from His kamandalu washed Lord Trivikrama’s feet. And that water came down as Ganga.
Actually, it was in Devaloka earlier. Later, Bhagiratha, belonging to the Surya Vamsha, did penance to bring Ganga down to earth. That’s why Ganga is also known as Bhagirathi. Ganga came down with great force, washing away everything that came in its way. Lord Shiva stored this Ganga in His jataa. That’s why He is known as Gangadhara. On being prayed to by Bhagiratha, Lord Shiva released the Ganga. It came down and washed away Sage Janhu’s hermitage and his sacrificial arena. In anger, Sage Janhu drank all the Ganga water. And then afterwards left it; that’s why Ganga is known as Janhavi or Janhu-Kanya.
Like this, the Ganga is flowing in our country and then merges with her husband, which is the Samudraraja or Varuna. Ganga, in another form, is present in the devaloka. This was the Ganga in which Dharmaraja took a dip and lost all his human traces and became equal to Yama Dharmaraja in all qualities. Means you can imagine how pure this Ganga is. Shanideva, while praising Narasimha, in the Bhavishyottara Purana says:
यत्पादपंकजरजः परमादरेण संसेवितं सकलकल्मषराशिनाशम् ।
कल्याणकारकमशेषनिजानुगानां सत्त्वं नृसिंह मयि देहि कृपावलोकम् ॥
O Lord Narasimha, the dust of whose lotus feet is served with the highest devotion, which destroys the heap of all sins, and which brings ultimate welfare to all His followers—please grant me Your merciful and compassionate glance.
If worshipping Bhagavan’s feet with the highest devotion itself burns away all kinds of sins, then why cannot His charanamrit, which is so pure, burn our sins? But a dip alone won’t work. You must do it with what is known as anusandhaana. Anusandhaana means to contemplate the greatness of the Ganga and Her father, which is Bhagavan Vishnu. Plus, with that Bhakti, if you have a dip in the Ganga, then only it would remove sins; otherwise, it would be just a normal bath in the Ganga. Within the Ganga, there is the special presence of Bhagavan Vishnu. It is not just a river but Devi who is present in the form of a river.
This Ganga is the wife of Varunadeva. She wears a crown full of gems, diamonds, and gold. She has a kumkuma tilaka on Her forehead. She has eyes in the shape of lotus petals and is very beautiful to look at. She has a hair bun behind, which is decorated with flowers with great fragrance. She is holding Vara and Abhaya Mudra in Her hands (Vara means Ashirvaad mudra and Abhaya Mudra means inverted Ashirvaada Mudra for providing protection). In the other two hands, She is holding Shankha and Chakra, and is riding on a crocodile. This is the picture of Ganga Devi, who was born from the lotus feet of Lord Vishnu.
[Picture of Ganga Devi as I described earlier and as per the shaastras]
Therefore, Ganga can wash all our sins because it is Hari Paadodaka, and hence it has the power to destroy all our sins and make us pure. But one should not take it to be granted that I would commit sins, go, take a dip in Ganga, again commit sins, and have a dip in Ganga. That won’t destroy your sins. With a pure mind and devotion towards Bhagavan Vishnu, if one has a bath in Ganga, it would remove all his/her sins, because he/she is doing Hari-naama smarana; plus, it is Ganga, which is Vishnu Paadodaka; it will cleanse all the dirt present in him/her.
Just by chanting the name ‘Ganga, Ganga’ itself, will destroy all your sins, even if you are yojanas away from Ganga. Even if you say, ‘Ganga Ganga’ keeping a hand on your Kalasha, Ganga will come and have Her divine presence in the Kalasha. If this is the glory of just the name ‘Ganga’ , then imagine, how effective the river itself might be, and how great the father of that river, Lord Vishnu might be?
गंगा गंगेति यो ब्रूयाद् योजनानां शतैरपि ।
मुच्यते सर्वपापेभ्यो विष्णुलोकं स गच्छति ॥
Chanting "Ganga, Ganga" from any distance liberates one from all sins, leading them directly to Lord Vishnu's supreme abode.
[Skanda Purana]
सञ्चिन्तयेद्भगवतश्चरणारविन्दं
वज्राङ्कुशध्वजसरोरुहलाञ्छनाढ्यम् ।
उत्तुङ्गरक्तविलसन्नखचक्रवाल-
ज्योत्स्नाभिराहतमहद्धृदयान्धकारम् ॥ २१ ॥
यच्छौचनि:सृतसरित्प्रवरोदकेन
तीर्थेन मूर्ध्न्यधिकृतेन शिव: शिवोऽभूत् |
ध्यातुर्मन:शमलशैलनिसृष्टवज्रं
ध्यायेच्चिरं भगवतश्चरणारविन्दम् ॥ २२ ॥
The devotee should first concentrate his mind on the Lord’s lotus feet, which are adorned with the marks of a thunderbolt, a goad, a banner and a lotus. The splendor of their beautiful ruby nails resembles the orb of the moon and dispels the thick gloom of one’s heart. The blessed Lord Śiva becomes all the more blessed by bearing on his head the holy waters of the Ganges, which has its source in the water that washed the Lord’s lotus feet. The Lord’s feet act like thunderbolts hurled to shatter the mountain of sin stored in the mind of the meditating devotee. One should therefore meditate on the lotus feet of the Lord for a long time.
[SrimadBhagavatam, Tritiya Skanda Chapter 28]
If this is the glory of Ganga, the Paadodaka of Vishnu, then why cannot it destroy all our sins??
Hope this helps!
Jay SriRam!
ShriKrishnarpanamastu!