More than any other resource limit, the availability of freshwater might be poised to rush up on us the soonest. Unlike energy, there is a clear limit to the amount of freshwater on Earth – and an even tighter limit on the amount that is available for human use (some is dirty, or locked up in ice caps – and ecosystem functions need their share too). And unlike oil, water is immediately necessary for human survival, and a limiting factor in food production.

The expected effects of climate change on global rainfall patterns might be the most inconvenient of them all. Warmer temperatures are projected to drive precipitation extremes even further, making dry places drier and wet places wetter.  So if your region is drought-prone now, look out. Otherwise buy an umbrella. Here are two maps to illustrate the point: the first is a map of currently water-stressed areas highlighted in red, and the second is a map of expected percentage change in precipitation for the period 2090-2099, relative to 1980-1999.

Current water stress levels, from 1995 data.

Projected changes in precipitation, from Dec-Feb & Jun-Aug, for 2090-2099, as a result of climate change.

Now imagine laying map #2 over map #1. All the areas in red – the regions expected to be hardest hit by drought – are the spots already stressed by water scarcity. “Inconvenient” is one way of putting it. And this, I think, is before factoring in the extra pressure on water resources exacted by world population growth. To get a sense of the population factor, here are maps of the “annual renewable water supply per person by basin for 1995 and projections for 2025.” And that’s minus climate change.

This interview with Steven Solomon, author of the new book, Water: The Epic Struggle for Wealth, Power, And Civilization, is a reminder to yours truly in the comfortably water-rich Great Lakes region that scarcity isn’t merely a scientist’s projection. It’s already happening. And “epic” it certainly seems to be. Ice pack high in the Himalayas , whose spring thaws give life to nearly 3 billion people, has shown recent signs of recession. According to Solomon, such a disruption might have riotous effects in places like already-fragile Pakistan, who may see “one third of its water from in the Indus River—its main water lifeline—dry up from the lost glacier melt. At the same time, its population is increasing by 30 percent. So in the next 15 years, we can imagine a country that’s already on the brink, dealing with a loss of 30 percent of its water while the population increases by 30 percent.”

Bad news. Because water scarcity is the ultimate existential problem: if you’re thirsty, you need it now. That’s playing out in Haiti currently, where the unfolding humanitarian crisis there has, in some instances, expressed itself in violent skirmishes over drinking water. Haiti’s population is about 9 million; a dry Ganges is about 333 times worse.

So: fresh water availability is starting to look like the first cement wall that’s awaiting both economic and population growth – and one that’s spatially discrete but globally relevant.

Notes on the Visuals

I’ve been getting more and more interested in the way visualizing data can help tell stories, so I spent much of this weekend hunting around for a map that overlays future rainfall projections on to a map of current water availability. Nada. Does the data exist for such a map? Has no one produced it? Or do my internet research skills need polishing? Finding nothing, I figured I’d mine rainfall data from the IPCC, UNEP or UNDP – but no machine-readable data seems to be out there. Am I missing something?

If data on these topics isn’t readily available, I hope someone pushes for their availability – because getting such things into the hands of the public could make for some interesting new insights into the challenges that lie ahead. For those curious, I did find ClimateWizard.org, a very cool web project that comes close to what I just described. These guys have made available customized interactive maps of climate projections – but with kinda tight legal stipulations on use. No Creative Commons out there for climate data?

If you know of machine-readable data sets along these lines, please shoot me an email or leave a comment below. I’d love to try my hand at some original map overlays!!

The maps above come from the very helpful offerings of WRI’s EarthTrends and the IPCC. Find the first here and the second here (on page 16 of the pdf).

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