The Kanvar Pilgrimage--Overview
The Kanvar Mela is a festival in which pilgrims draw water from Hardwar (or some other place) and carry it a temple (often in their home village) as an offering to Shiva. One of these festivals is in late winter (before Shivaratri) and the other during Shravan (monsoon). Pilgrims time their departures to arrive on particular festival days.
Pilgrims tend to travel in groups, and each group enforces particular rules on its members These can vary considerably, especially with regard to ritual purity. Yet one of the most common rules is that once the water vessels have been placed in the kanvar, it cannot touch the ground again. I believe that this prohibition comes from the charter myth of Vaidyanath Dham in Jharkhand, in which Ravana placed a Shiva linga on the ground, and it stuck fast in place (pilgrims there also carry Ganges water as an offering to Shiva).