Ganggavisarjanamurti is the Lord Shiva himself, known for releasing Goddess River Ganga from his matted hairs. He is also known as Gangadhara Murthi for bearing Ganga on his head.
The Sanskrit word ‘Visarjana’ means to release. Lord Shiva is known for his unique nature, for being only the God who bears Ganga in two ways. One in withstanding the forceful flow of River Ganga from the heavens, and in the other way in releasing the River Ganga from his hair with the force not disturbing the mankind on the earth.
The story and the reason behind Lord Shiva releasing Ganga is the king Bhageeratha. The King Bhageeratha was committed to purify the souls of his ancestors by making Ganga flow through their ashes. He made severe penance towards Brahma and finds out that it’s only Lord Shiva who can bear the flow of Celestial Holy River Ganga and bring it down to earth. So Bhageeratha performs the penance towards the Gods and Goddesses to bring the Holy River to the earth.
In the first attempt, he performs the penance towards the Lord Shiva and River Ganga, makes the Lord to bear Ganga over his head in his matted hair. In the next attempt, he performs the penance towards the Lord Shiva and pleads him to release the river to the earth without affecting the other beings and flow across the ashes of his ancestors.
Thus making Lord Shiva release the holy River Ganga onto the earth, the Lord Shiva is being called as Ganggavisarjanamurti.