The Washington Post reports: As India, the world’s second-most populous country, reels from an intense drought, the World Bank has released a new report finding that perhaps the most severe impact of a changing climate could be the effect on water supplies.

The most startling finding? The report suggests that by 2050, an inadequate supply of water could knock down economic growth in some parts of the world a figure as high as 6 percent of GDP, “sending them into sustained negative growth.” Regions facing this risk — which can at least partly be averted by better water management, the document notes — include not only much of Africa but also India, China and the Middle East.

“When we look at any of the major impacts of climate change, they one way or another come through water,” said Richard Damania, a lead economist at the bank and the lead author of the report, on a call with reporters Tuesday. “So it will be no exaggeration to claim that climate change is really in fact about hydrological change.”

Climate change hits water supplies in multiple ways. Warm temperatures can cause more evaporation of water from landscapes, while changes in precipitation can lead to both more intense individual downpours but also swings into drought conditions. The threat from all this is not just to what people drink but what they eat: The human activity that consumes the most water is agriculture.

And then, there’s sea-level rise: It can push into coastal aquifers, as is happening today in the state of Florida, and thus threaten to make them more saline and less usable for human needs. So it isn’t only surface waters that may be depleted by climate swings, but also groundwater.

The World Bank report says that 1.6 billion people on Earth already live in nations that are subject to water scarcity. [Continue reading…]