The custom of carrying Kanwar started in the Treta Yuga - the silver age
of Hindu mythology. Lord Rama had carried the holy ganges water from
Sultanganj in a kanwar and offered to Lord Shiva at Babadham.
Shravani Mela starts in every month of Sawan (Hindi Month) July-August Month . More then 50
lakhs devotees come Sultanganj for take Holy water of Ganga River.
After taking Holy water of Ganga River they go to Baidyanath Dham
(Deoghar) by on foot in full month of Sawan. The total distance from
Sultanganj to Baidynath Dham is 105 km. by old way and 90 km from new
shortcut way. The person who goes Babadham (Deoghar) from Sultanganj on foot they
called general Kanwariya. They reached Babadham in 3-4 days. The person
who started non stop on foot journey from Sultanganj to Babadham for 110
km they called 'Dak - Bam'.
Source:-shravanimela.blogspot.com