How the World Really Works: A Scientist’s Guide to Our Past, Present and Future

by Vaclav Smil

But most studies concur that demand-driven freshwater scarcity will have a much greater impact than the shortages induced by climate change. As a result, our best option for dealing with future water supply is to manage demand, and one of the best large-scale examples of this working is the recent history of the US’s reducing per capita water usage.63 In 2015, overall US water consumption was less than 4 percent higher than it was in 1965—but during the intervening 50 years the country’s population increased by 68 percent, its GDP (in constant monies) more than quadrupled, and irrigated farmland increased by about 40 percent. This means that average per capita water use decreased by nearly 40 percent, that the water intensity of the US economy (units of water per unit of constant GDP) declined by 76 percent, and, as the total volume of water used for irrigation was actually slightly lower in 2015, that applications per unit of farmland declined by nearly a third. There are, of course, physical limits to the further reduction in all of these uses of water, but the US experience shows that the gains can go far beyond marginal ones.