The Ganga (Ganges) is a transboundary river with headwaters in the Hindu Kush Himalayan region (Figure 1). It begins at the confluence of the Bhagirathi and Alaknanda at Devaprayag in the Tehri Garhwal district of Uttarakhand in India and flows for almost 2,500 kilometres through India and Bangladesh before emptying into the Bay of Bengal (NIH/GOI 2015). The Alaknanda itself has five confluences before joining the Bhagirathi, the last of which is the confluence with the Mandakini at Rudraprayag. The river has many major tributaries, with the Tons (Tamsa), Gandaki, Yamuna, and Koshi among the most important. The Ganga river emerges from the mountains at Rishikesh and enters the plains at Haridwar, also in Uttarakhand.