介绍： Water scarcity: Liquidity crisis
As water becomes ever more scant the world needs to conserve it, use it more efficiently and establish clear rights over who owns the stuff
From The Economist 20161105

Audio:

0:00




“NOTHING is more useful than water,” observed Adam Smith, but “scarcely anything can b...

介绍： Water scarcity: Liquidity crisis
As water becomes ever more scant the world needs to conserve it, use it more efficiently and establish clear rights over who owns the stuff
From The Economist 20161105

Audio:

0:00




“NOTHING is more useful than water,” observed Adam Smith, but “scarcely anything can be had in exchange for it.” The father of free-market economics noted this paradox in 18th-century Scotland, as rain-sodden and damp then as it is today. Where water is in ample supply his words still hold true. But around the world billions of people already struggle during dry seasons. Drought and deluge are a costly threat in many countries. If water is not managed better, today’s crisis will become a catastrophe. By the middle of the century more than half of the planet will live in areas of “water stress”, where supplies cannot sustainably meet demand. Lush pastures will turn to barren desert and millions will be forced to flee in search of fresh water.

Where water is available, when and in what condition matters hugely. About 97% of the water on earth is salty; the rest is replenished through seasonal rainfall or is stored in underground wells known as aquifers. Humans, who once settled where water was plentiful, are now inclined to shift around to places that are less well endowed, pulled by other economic forces.

Climate change is making some parts of the planet much drier and others far wetter. As people get richer, they use more water. They also “consume” more of it, which means using it in such a way that it is not quickly returned to the source from which it was extracted. (For example, if it is lost through evaporation or turned into a tomato.) The big drivers of this are the world’s increased desire for grain, meat, manufactured goods and electricity. Crops, cows, power stations and factories all need lots of water.

To make matters worse, few places price water properly. Usually, it is artificially cheap, because politicians are scared to charge much for something essential that falls from the sky. This means that consumers have little incentive to conserve it and investors have little incentive to build pipes and other infrastructure to bring it to where it is needed most. In South Africa, for example, households get some water free. In Sri Lanka they pay initially a nominal 4 cents for a cubic metre. By contrast, in Adelaide in Australia, which takes water conservation seriously, an initial batch costs $1.75 per cubic metre. Globally, spending on water infrastructure faces a huge funding shortfall. A hole of $26trn will open up between 2010 and 2030, estimates the World Economic Forum, a think-tank.

In many countries people can pump as much water as they like from underground aquifers, because rules are either lax or not enforced. Water use by farmers has increased sharply in recent decades (see chart). This has allowed farmers to grow huge amounts of food in places that would otherwise be too dry to support much farming. But it is unsustainable: around a fifth of the world’s aquifers are over-exploited. This jeopardises future use by causing contamination. It also damages the layers of sand and clay that make up aquifers, thereby reducing their capacity to be replenished.

People do not drink much water—only a few litres a day. But putting food on their tables requires floods of the stuff. Growing 1kg of wheat takes 1,250 litres of water; fattening a cow to produce the same weight of beef involves 12 times more. Overall, agriculture accounts for more than 70% of global freshwater withdrawals.

And as the global population rises from 7.4bn to close to 10bn by the middle of the century, it is estimated that agricultural production will have to rise by 60% to fill the world’s bellies. This will put water supplies under huge strain.

Food for thought

Extravagance must be tamed. Farmers produce far more food than finds its way into stomachs. Some estimates suggest that as much as a third of all food never actually makes it to a plate, wasting as much water as flows down Russia’s Volga river in a year. Richer households are responsible for throwing out the largest share of unwanted victuals. Poorer ones may never even see the produce that rots on slow, bumpy journeys to market.

Water is vital not only for food and domestic well-being. It is “fundamental to economic growth”, points out Usha Rao-Monari, head of Global Water Development Partners, an investment outfit backed by Blackstone, a private-equity giant. Scarcity stalls industrial development by squeezing energy supplies. Electricity generation depends upon plentiful quantities; nuclear power requires water both for cooling turbines and the reactor core itself, for example. Coal-fired plants cannot function without it.

Power generation is a thirsty business. Overall about 41% of America’s withdrawals go towards cooling power stations. In countries such as Brazil, where hydroelectric power provides more than two-thirds of the country’s needs, scarcity is also a worry, particularly when dam designs rely on rivers fed by rainfall (see article). Spikes in energy prices often follow dry periods. Zambia endured sporadic blackouts that began a year ago and lasted until April, when drought crippled power generation from the Kariba dam.

As poor countries develop, global demand for electricity from industry is expected to increase by 400% over the first half of the 21st century. The majority of water-intensive industries, such as coal mining, textiles and chemicals, are found in countries that are particularly prone to water shortages: China, Australia, America and India. Industry can increase strains on supplies too, by polluting water, making it unfit for human use. Over a third of China’s waterways have been spoiled by industrial effluent and other nasties.

Climate change will only make the situation more fraught. Hydrologists expect that a warming climate will see the cycle of evaporation, condensation and precipitation speed up. Wet regions will grow wetter and dry ones drier as rainfall patterns change and the rate increases at which soil and some plants lose moisture.

Deluges and droughts will intensify, adding to the pressure on water resources. Late or light rainy seasons will alter the speed at which reservoirs and aquifers refill. A warmer atmosphere holds more moisture (the water content of air rises by about 7% for every 1ºC of warming) increasing the likelihood of sudden heavy downpours that can cause flash flooding across parched ground. This will also add to sediment in rivers and reservoirs, affecting storage capacity and water quality.

Less snow in a warmer world creates another problem. Places such as California depend upon mountain meltwater flowing down in time for summer. Climate change will make the availability of water more variable in Southern Africa, the Middle East and America. The World Resources Institute, a think-tank, ranked 167 countries, and found that 33 face extremely high water stress by 2040 (see map).


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