India, May 12 -- 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 that the water flow could rise over the next couple of decades and then fall. Already, in this time of relative plenty (considering what is to come), everybody wants more, especially in the dry season. Pakistan's Punjab wants more - sparking off protests in downstream Sindh. Pakistan, wary of any potential lessening, complains about Indian dams built on the western rivers - a neutral expert has deemed that the dams' designs abided by the now-in-abeyance Indus Waters Treaty (IWT). The current infrastructure cannot hold back water for too many days in May. But they can add to the confusion, especially when no intimation needs be provided to the downstream party. But, when the water pie shrinks, which it will, it won't shrink uniformly. As leading glaciologist, Dr Anil Kulkarni, recently said, the glaciers feeding the three eastern rivers - the Ravi, Sutlej, and Beas - are not only much smaller than those feeding the western rivers, they are also melting faster. The water pie to be shared between India and Pakistan - already more lopsided than the superficially-fair 'you take three, we take three' terms of the IWT suggest - will become far more unequal in the future. India, with its dry northwest, is unlikely to accept this division, especially in the current circumstances. The division of such water amongst the India's northwest states is another matter, as is the division between Punjab and Sindh in Pakistan. Those fights are like rearranging the deck chairs on the Titanic and will have to wait another day for their resolution. It's worthwhile asking how the Indus waters are used. Much of this flows into Pakistan, where much of it flows into fields. As per a 2019 World Bank Report, "Pakistan is in the lowest 5% of countries in terms of water productivity", and "is in the highest decile of countries in terms of water stress". Water productivity is the economic output per unit of water withdrawn from the environment. Not a comforting thought. That India is also water-scarce adds an edge to this water-sharing. Given current economic incentives and voter preferences, this inefficiency is unlikely to change, and given the climate crisis and demographic realities, the scarcity will get worse. Something's got to give. Pakistan could up its water efficiency game (the World Bank has a slew of suggestions); it could also give more water to Sindh. It could appeal to the World Bank and others to exert pressure on India, as they once did. But the World Bank president, in response to a question on whether they would intervene in the treaty's abeyance, recently responded, "No, we're not.there's a lot of speculation in the media on whether we'll fix it or not. it's all bunk!". India could build additional infrastructure to divert the water to its own dry northwest, where this largesse would be welcomed with open arms. Pakistan, with its life on the line, is unlikely to sit quietly by. It could turn to its iron-friend for help, the one that is 'upstream-est' of them all. Or indeed, begin to look to an erstwhile part of itself in the east, putting new pieces in play in the subcontinental water theatre. All the while, the world warms. In this scenario, improving its own water productivity, as unsexy as that sounds, is India's best defence....