At 4238 m above sea level, the Bhagirathi glacier begins at Chaukhamba to merge into the Gaumukh. Owing to its mineral content and the terrain of medicinal plants through which it flows, it is believed that the Ganges water is extremely pure and therapeutic.
So much so that it is believed that even when it is kept for years, the water doesn't become contaminated. You can also trek up the glacier to reach Nandanvan, Tapovan and Gaumukh.
Ask a question from the travellers who have experience.