India, May 11 -- Perspective is a useful thing. Open Google Earth and zoom out a few thousand kilometres. Around the 30degN latitude, you will see a band of sand stretching across the Earth. The Thar Desert lies here, as do large parts of Pakistan - only, there is a thick green ribbon swirling through that country, thanks to the largesse of the Himalayan glaciers. The contrast between sand and green shows, more than any number ever could, how much Pakistan needs the Indus waters. They will not survive without it.

The Indus system, more than the Ganga and the Brahmaputra systems, depends on glacier- and snow-melt for its waters, which, in turn, increases its climate vulnerability. What happens when these glaciers melt? Studies suggest tha...