The two main headstreams of the Ganga River are the Bhagirathi and the Alaknanda. The Bhagirathi originates from the Gangotri Glacier in Uttarakhand, specifically from a subglacial meltwater cave at Gaumukh, while the Alaknanda rises near the Himalayan peak of Nanda Devi in Uttarakhand as well

. These two rivers meet at a place called Devprayag in Uttarakhand. At this confluence, the Bhagirathi and Alaknanda unite to form the main stream known as the Ganga River

. In summary:

• Headstreams: Bhagirathi and Alaknanda
• Confluence point: Devprayag, Uttarakhand
• Formation: Their meeting at Devprayag marks the beginning of the Ganga River proper