Explanation:

Dhauliganga originates from Vasudhara Tal, perhaps the largest glacial lake in Uttarakhand. 

• Dhauliganga is one of the important tributaries of Alaknanda, the other being the Nandakini, Pindar, Mandakini and Bhagirathi.
• Dhauliganga is joined by the Rishiganga river at Raini. It merges with the Alaknanda at Vishnuprayag.
• There it loses its identity and the Alaknanda flows southwest through Chamoli, Maithana, Nandaprayag, Karnaprayag until it meets the Mandakini river, coming from the north at Rudraprayag.
• After subsuming Mandakini, the Alaknanda carries on past Srinagar, before joining the Ganga at Devprayag near.
• Alaknanda then disappears and the mighty Ganga carries on its journey, first flowing south then west through important pilgrimage centres such as Rishikesh and finally descending into the Indo-Gangetic plains at Haridwar.

Hence only statement 1st is correct.