The mishap occurred at about 1:30 pm at Shivpuri under Muni Ki Reti police station in Tehri district, 18 kms from Rishikesh, SHO Rajiv Dandariyal said.
All the six tourists were saved by 40-year-old Ram Kumar Pathak but he himself could not survive as too much water had flown into his system causing asphyxiation.
After Pathak somehow managed to reach the river bank, he was rushed to a government hospital in Rishikesh where doctors declared him dead, the police official said.
Pathak was accompanying the team of rafters as a guide from Marine Drive, the river point from where they began their expedition this morning, he said.
A similar rafting mishap at Wall Rapid in the Ganga near Vyasi had claimed two lives at Vyasi a fortnight ago.