According to AGNI-PURANA which is a holy ritual, wherever the water of the ganga reaches that place becomes sacred, and clean from all evils and above all it is sacred. It is supposed that a few drops of Ganga Jal makes everything Holy ...pavitra. Ganga is the holiest river to all Hindus. Ganga Jal is considered as one of the holiest "Upachar" of any Hindu Puja or Pooja.  In any 'Puja' (Worship to God & Goddess) this 'GANGA JAL' (Ganga water) is utmost required. But People who is away from the river Ganga, can not get this holy water easily and as a matter of fact they have to worship God & Goddess without it. 

Ganga has a long theological history too.   Ganga water has certain chemical qualities. Many chemical & scientific tests have been carried out with Ganga water and now it has been scientifically proved that Ganga water enriched with some extraordinary properties. Indian environmental engineers confirmed that Ganga water has a super self-cleaning properties. Its seen that this water does not deteriorate largely even for years after year if its kept in a closed vessels due its self cleaning properties. Scientifically it's also seen that Ganga water Soil (soil on the bank of Ganga river) has got medicinal effect. Ganga jal also perhaps got this effect and that's why a man can keep Ganga Jal for a long days in any bottle.