It's just not water alone--though it's important enough for who survives without water?--but its unique properties. DS Bhargava of University of Roorkee found Ganga to decompose organic waste at a 15-25 rates faster than any other river of the world.
New Delhi's Malaria Research Center claimed that water taken from Gange's upper ambit prevented mosquito breeding. British bacteriologist Ernest Hanbury Hankin found out in 1896 that Vibrio Cholerae, a deadly bacterium known to spread cholera, was killed within three hours after it was added in water from Ganga. He eventually concluded that Ganga--and Yamuna--have been largely responsible for preventing the spread of cholera.
Swami Sanand's death to Gangaji's cause was not the first one. Swami Nigmananda had died for a similar cause, seven years ago in 2011. Swami Sanand had famously predicted that Swami Nigmananda's death would make 10 Nigmanandas sacrifice their lives. He himself was to be the next in line. The people we choose to effect the change, however, remain indifferent. Ganga remains a dump of our waste. Nothing but a mass resistance would do if Ganga, or India, is to survive.
1- https://www.youtube.com/watch?v=F7rW0nNkxwU (23.51-24.05)