India, March 20 -- Economists speak of capital, ecologists of ecosystems. But, perhaps, one of our most underappreciated assets is water, gurgling through pipes, feeding fields, and supporting the livelihoods of a sizeable portion of our population through agriculture, environment, and related activities. Yet it is vanishing faster than we can replenish it. There is no bail out with a stimulus policy here. What we can do is learn to live differently, treating water not as a commodity to be consumed but as a global commons to be cared for.

Water covers two-thirds of the planet, but less than 3% is fresh, and even that is unevenly shared. Urbanisation, population growth, and competing demands are testing the limits of this resource. India,...