Water- Another Global Crisis?

By Richard Black
Environment correspondent, BBC News

Last year the Intergovernmental Panel on Climate Change (IPCC) took an in-depth look at how the raw availability of water might alter in the future as climatic patterns change.

Its projections are derived from computer models of the Earth’s hugely complex climate system, and as such are far from being firm forecasts.  A warmer climate overall means a wetter climate; warmer air can hold more moisture.

Mountain glaciers act as “natural reservoirs” Himalayan glaciers alone store water used by more than a billion people Scientists measure the volume of glaciers in “mm SLE” – the amount that sea levels would rise if the ice melted

But weather patterns are likely to shift, meaning that water will be deposited in different places with a different pattern in time.

“In general we see drying in the sub-tropics and mid-latitudes, from southern Europe across to Kazakhstan and from North Africa to Iran,” recounts Martin Parry, who as co-chair of the IPCC’s working group on climate impacts oversaw the water report’s compilation.

“And the drying extends westwards into Central America. And there are equivalents in the southern hemisphere – southern Africa, Australia.”

In some populated parts of North Africa and Central Asia, he says, people may struggle simply to get enough to drink.

Other areas, meanwhile, are projected to receive more rain – considerably more, in some cases.

The question then is whether societies can make use of it.

“If you look at India, Bangladesh and Burma, there are indications of an increase in water availability,” says Professor Parry.

“But when you look in more detail you see that monsoonal precipitation will become more intense – there’ll be a heavier downpour but over fewer days – so you might just end up with more runoff, which could actually mean less availability of water to the community.”

Thirsty work

A changing climate is only one of the factors likely to affect the amount of water at each person’s disposal in future.

A more populated world – and there could be another 2.5 billion people on the planet by 2050 – is likely to be a thirstier world.

Those extra people will need feeding; and as agriculture accounts for about 70% of water use around the world, extra consumption for growing food is likely to reduce the amount available for those basic needs of drinking, cooking and washing.

Industry can also take water that would otherwise have ended up in peoples’ mouths.

FUTURE WATER STRESS Interactive map: Water stress in a changing world

On the other hand, as a society industrialises it tends to become less reliant on farming – which could, in principle, reduce its local demand.

It is a tremendously complex picture; and forecasting its impacts makes simple climate modelling look a trivial task by comparison.

Researchers at the University of Kassel in Germany, led by Martina Floerke, have attempted it.

Their projections suggest that some regions are likely to see drastic declines in the amount of water available for personal use – and for intriguing reasons.

“The principal cause of decreasing water stress (where it occurs) is the greater availability of water due to increased annual precipitation related to climate change,” they conclude.

“The principal cause of increasing water stress is growing water withdrawals, and the most important factor for this increase is the growth of domestic water use stimulated by income growth.”

The modelling suggests that by the 2050s, as many as six billion people could face water scarcity (defined as less than 1,000 cubic metres per person per year), depending, most importantly, on how societies develop – a significant increase on previous estimates.

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Source:  BBC News